Groundwater Quality Near Riverbanks and Its Suitability for Agricultural Use in Semi-Arid Regions

Abstract

Water scarcity has become one of the most pressing challenges to agricultural sustainability, particularly in arid and semi-arid regions where climate change, dam construction, and rapid population growth have intensified the pressure on water and food resources. Groundwater adjacent to rivers represents a potential supplementary resource that can reduce reliance on restricted surface water supplies. This study assessed the hydrochemical characteristics and agricultural suitability of shallow groundwater located near the Tigris River, Iraq. Fieldwork involved monitoring four active wells and collecting samples over six periods from October 2022 to May 2023, combined with twelve soil samples from surrounding agricultural fields. Laboratory analyses determined key water and soil properties, including pH, electrical conductivity, major cations and anions, and a range of salinity and sodicity indices such as total dissolved solids (TDS), sodium adsorption ratio (SAR), residual sodium carbonate (RSC), potential salinity (PS), magnesium ratio, Simpson ratio (SR), Jones ratio (JR), and sodium percentage (Na%). Results indicated that groundwater levels fluctuated seasonally in tandem with the Tigris River, which directly influenced salinity levels. SI values were positive, TDS values were in the high salinity class, RSC values were consistently negative, PS values were in the medium to poor category, Na% values and MR values were within acceptable limits for irrigation, and SR values were moderately to highly contaminated. Groundwater quality, according to the U.S. Salinity Laboratory classification, was categorized between the C4S1 class (very high salinity, low sodium) and the C3S1 (high salinity, low sodium). Soil analyses showed predominantly light-textured soils with moderate Ec and SAR values below sodicity thresholds. The combination of soil permeability and groundwater characteristics suggests that irrigation is feasible under specific management practices. The study concludes that groundwater adjacent to rivers can serve as a valuable supplementary source for agriculture in semi-arid regions. Its use is most effective when applied to salt-tolerant crops, supported by leaching requirements, or blended with fresh water. These findings emphasize the importance of integrated groundwater management for enhancing agricultural resilience and sustainable land use under water-scarce conditions. Excessive extraction of groundwater near rivers can also pose long-term sustainability challenges.

1. Introduction

Water is a fundamental resource for sustaining ecosystems, agricultural production, and human societies. In recent decades, however, water scarcity has emerged as one of the most pressing challenges to global food security and sustainable development. Climate change has intensified the frequency and severity of droughts, altered rainfall regimes, and increased evapotranspiration rates, especially in arid and semi-arid regions [1,2]. At the same time, rapid population growth and urban expansion have amplified water demand, placing unprecedented pressure on both surface and groundwater resources [3,4]. The combined effects of these drivers have resulted in widespread land degradation and desertification, threatening agricultural systems that depend heavily on irrigation.

Among the most vulnerable areas are riparian and alluvial plains, where agricultural production is closely linked to river systems. Although rivers provide relatively high-quality surface water, access is often constrained by legal, political, and hydrological factors, including water-sharing agreements, upstream dam construction, and seasonal fluctuations in flow [5]. In the Middle East, transboundary water governance is particularly critical, as countries such as Iraq depend heavily on inflows from upstream nations. Regulation of the Tigris and Euphrates Rivers has reduced downstream water availability, resulting in diminished irrigation potential and an increased reliance on alternative water sources [6]. The accelerating depletion of surface water sources, coupled with rising agricultural water requirements, has intensified the need to explore alternative water supplies. In many arid and semi-arid regions, including central Iraq, groundwater represents the most accessible and vital reserve for sustaining agricultural production. However, its long-term viability depends on understanding how soil characteristics and hydrochemical conditions interact to influence water quality and land productivity. In this context, the present study addresses the research problem of how groundwater quality and soil properties co-evolve in river-adjacent agricultural lands subjected to fluctuating hydrological conditions. The study aims to evaluate the spatial and seasonal variability of groundwater chemistry, investigate its relationship with soil physico-chemical properties, and assess the implications for irrigation suitability and soil sustainability. These objectives are framed within the broader goal of improving water resource management in arid environments where surface and subsurface water systems are strongly interlinked.

Groundwater has become indispensable for sustaining agriculture under such conditions. It serves as a buffer during dry periods, supports crop production when surface water is restricted, and contributes to stabilizing rural livelihoods [7,8]. Yet the suitability of groundwater depends strongly on its quality, which is influenced by geological formations, hydrological interactions, and anthropogenic activities such as irrigation return flows and fertilizer application. However, groundwater may be contaminated with toxic heavy metals from multiple sources, whether natural factors such as volcanoes and rock weathering or human activities such as agriculture and industry, which may affect its quality [9]. Salinity and sodicity are among the most critical parameters determining groundwater usability. Excessive salt concentrations reduce plant growth, while sodium-rich water can degrade soil structure, lower permeability, and accelerate desertification processes [10,11].

A wide range of hydrochemical indices has been developed to evaluate irrigation water quality. These include electrical conductivity (EC) and total dissolved solids (TDS) for assessing overall salinity hazards; sodium adsorption ratio (SAR), residual sodium carbonate (RSC), and sodium percentage (Na%) for sodicity risk; as well as composite indices such as potential salinity (PS), magnesium ratio (MR), Simpson ratio (SR), and Jones ratio (JR), which account for specific ion effects and water–soil interactions [12,13,14,15]. Together, these indicators provide insights into the long-term impacts of irrigation water on soil fertility, drainage requirements, and crop selection.

In Iraq, the alluvial plains of the Tigris and Euphrates are among the most agriculturally productive areas but are increasingly threatened by declining water quality. Previous studies have shown that underwater in these regions are often saline and unsuitable for sensitive crops [16]. However, groundwater in areas immediately adjacent to rivers may differ significantly in quality due to lateral seepage from fresh river water and interactions with relatively permeable soils [17]. These riverbank aquifers could provide an important supplementary source for irrigation, particularly if water is used strategically, for example, by alternating with surface water or blending with fresh supplies.

Despite its potential, the quality of groundwater adjacent to rivers in Iraq has not been thoroughly investigated. Most prior studies have focused either on regional hydrogeology or on groundwater salinity at broader scales, overlooking the localized dynamics of shallow aquifers in riparian zones [18]. Yet these environments are unique in that groundwater quality is shaped by seasonal river fluctuations, soil–water exchanges, and human management practices. A better understanding of these processes is essential for developing sustainable strategies that mitigate soil salinity, optimize water allocation, and protect agricultural productivity in semi-arid landscapes.

The present study addresses this knowledge gap by examining shallow groundwater adjacent to the Tigris River in Wasit Governorate, central Iraq. The area is particularly relevant because it combines fertile alluvial soils with increasing water scarcity and is representative of broader challenges across the Middle East. By integrating hydrochemical analysis of groundwater with soil characterization and seasonal monitoring, the study provides a comprehensive evaluation of the suitability of riverbank groundwater for irrigation.

This research (i) contributes to global debates on water scarcity by evaluating the hydrological connectivity and sustainable use potential of riverbank aquifers as irrigation sources under climate stress; (ii) advances regional understanding of groundwater–soil interactions in Iraq, where reduced river flows increasingly jeopardize agricultural sustainability; and (iii) provides a methodological framework that combines chemical indices, soil properties, and hydrological observations, offering insights transferable to other semi-arid regions. Finally, the findings have practical implications for water managers and policymakers seeking to balance food production with sustainable resource use. Adopting groundwater for irrigation can reduce pressure on surface water rather than on freshwater resources overall. It might also be worth noting that excessive groundwater extraction can create long-term sustainability challenges.

In addition to conventional salinity and sodicity concerns, recent studies have highlighted the potential mobilization of toxic elements, such as arsenic, lead, and chromium, in groundwater systems affected by variable redox and salinity conditions [9]. Although this study does not directly quantify these contaminants, acknowledging their possible occurrence is essential for framing the hydrogeochemical interactions observed in the region. It also emphasizes the importance of integrated monitoring programs that address both agronomic suitability and environmental safety.

The research tests the following hypotheses: (i) according to the USSL classification, groundwater quality adjacent to rivers exhibits lower sodicity but variable salinity due to continuous recharge from river water; (ii) seasonal fluctuations in the Tigris River strongly influence groundwater levels and EC in adjacent wells; and (iii) the combination of light-textured soils and moderate groundwater salinity reduces the risk of soil sodification, allowing the sustainable use of groundwater for salt-tolerant crops under proper management.

By testing these hypotheses, the study seeks to provide evidence-based recommendations for groundwater management strategies that enhance agricultural resilience in semi-arid environments. Rather than focusing solely on the exploitation potential of riverbank aquifers, this research emphasizes the assessment of their hydrological connectivity with adjacent rivers, the dynamics of groundwater recharge, and the determination of sustainable extraction limits. Understanding these processes is essential to ensure that groundwater use near riverbanks supports irrigation needs without compromising river discharge, ecological integrity, or long-term water security. The specific objectives of this study are to (i) characterize the hydrochemical properties of shallow groundwater in wells located near the Tigris River; (ii) assess the suitability of this groundwater for agricultural irrigation using internationally recognized salinity and sodicity indices; (iii) examine the influence of seasonal fluctuations in river water levels on groundwater depth and quality; and (iv) compare the chemical characteristics of groundwater and surface soil in river-adjacent agricultural lands to identify possible co-occurring patterns, rather than direct hydraulic interactions between them.

2. Materials and Methods

2.1. Study Area

The study was conducted in Wasit Governorate, central Iraq, within the grounds of Wasit University, which lies directly adjacent to the eastern bank of the Tigris River. This region is part of the Mesopotamian alluvial plain, characterized by fertile riverine soils, shallow groundwater, and an arid to semi-arid climate. Average annual rainfall in the area is low (<200 mm), concentrated in the winter months, while summer temperatures frequently exceed 45 °C, leading to high evapotranspiration rates and a strong seasonal water deficit.

Several shallow wells, with depths not exceeding 15 m, were drilled across the university campus in 2012 to provide supplementary irrigation for green spaces. Four wells were selected for this study based on their location and operational history: W1–W4 (Figure 1). These wells represent typical shallow aquifers hydraulically influenced by the Tigris River.

According to the United States Department of Agriculture (USDA) Soil Taxonomy, the predominant soils in the study area are entisols. They have been developed from recent river sediments and are generally light-textured, with loam and sandy loam as the dominant classes. Such soils have relatively high permeability and moderate organic matter content, making them suitable for both field crops and horticultural production, but also vulnerable to salinization under poor irrigation management. The geomorphology of the site, located on a river shoulder, facilitates groundwater recharge from both lateral seepage and irrigation return flows.

2.2. Sampling Design

Well water in the study area is only used during periods of critical need to irrigate some green spaces, grasses, and trees, particularly when fresh water from the Tigris River is unavailable. Groundwater samples were collected from the four wells at six intervals of 45 days over seven months: 1 October 2022; 15 November 2022; 1 January 2023; 15 February 2023; 1 April 2023; and 15 May 2023. On each sampling date, the static water level was recorded, and groundwater was pumped for 30 min before sampling to ensure representative water quality. Samples were stored in clean polyethylene bottles and transported to the laboratory for analysis.

In parallel, 12 composite soil samples were collected from multiple locations within the study area on 1 October 2022, from the surface layer (0–30 cm) at different locations within the study area, corresponding to fields and green spaces influenced by irrigation (Figure 1). The management style of these sites also differs in terms of the nature of their exploitation and management. Despite differences in land use, plant varieties, and their needs, they are similar in their method of using well water for irrigation, particularly when water from the Tigris River is unavailable. Sampling sites included agricultural fields, university gardens, and residential areas, coded as S1–S12. Samples were air-dried, sieved (2 mm), and prepared for chemical and physical analyses (Figure 2).

2.3. Laboratory Analyses

A 1:1 soil-to-water ratio (w/v) was used to prepare the soil extract for all chemical analyses, ensuring consistency and comparability with standard laboratory procedures. All results derived from the soil extract are expressed per liter of extractant solution. The standard deviation (SD) is reported for replicated measurements to reflect data variability and analytical precision. The pH, EC (ds m⁻¹), negative and positive ion values (meq L⁻¹), and SAR (mmol L⁻¹)^½) were estimated for both soil and groundwater, while the soil texture and exchangeable sodium percentage (ESP) values (%) were estimated specifically for soil. To measure pH, a Hanna pH 210 pH meter was used. EC (ds m⁻¹) was measured with a Hanna HI-2300 using calibrated electrodes [19]. Major cations (Ca²⁺, Mg²⁺, Na⁺, K⁺) and anions (Cl⁻, SO₄²⁻, HCO₃⁻, CO₃²⁻) were determined using titration, flame photometry, and turbidity methods as appropriate [20,21]. Soil particle size distribution (gm kg⁻¹) and soil texture (loam, L; sandy loam, SL; and sandy clay loam, SCL) were determined by the pipette method [21]. From the primary data, several indices commonly used to assess irrigation water quality were calculated, including:

SAR, using the Richards equation [20].

$$\mathrm{SAR}={\displaystyle \frac{Na+}{\sqrt{\frac{Ca+2+Mg+2}{2}}}}$$

(1)

ESP (%) was estimated according to the U.S. Salinity Laboratory (USSL).

$$\mathrm{E}\mathrm{S}\mathrm{P}={\displaystyle \frac{ 100(-0.0126+0.01475SAR)}{1+(-0.0126+0.01475\mathrm{S}\mathrm{A}\mathrm{R})}}$$

(2)

Residual Sodium Carbonate (RSC) (meq L⁻¹) [22]

RSC = (CO₃ + HCO₃) − (Ca²⁺ + Mg²⁺)

(3)

Adjusted Sodium Adsorption Ratio (SARadj) (mmol L⁻¹)^½) [13].

Adj SAR = SAR{1 + (8.4 − PHC)}

(4)

Potential Salinity (PS) (meq L⁻¹) [14].

PS = chloride ion concentration + 1/2 sulfate concentration

(5)

Magnesium Ratio (MR) (%) [23].

MR = (Mg²⁺ × 100)/(Ca²⁺ + Mg²⁺)

(6)

Sodium Percentage (Na%) [24].

Na% = ((Na⁺ + K⁺) × 100)/(Ca²⁺ +Mg²⁺ + Na⁺ + K⁺)

(7)

Simpson Ratio (SR) [15].

SR = Cl/(HCO₃ + CO₃)

(8)

Jones Ratio (JR) [25].

JR = Na⁺/Cl⁻

(9)

Theoretical carbonate equilibrium pH (pHc) and Saturation Index (SI) values were calculated from the relationship to the USSL:

Saturation index = pHa − pHc

(10)

And it was found (pHc)

pHc = (pK2 − pKc) + p(Ca² + Mg²)+ pAlk

(11)

where

• pHc = the pH at which water with a given calcium content and alkalinity is in equilibrium with calcium carbonate.
• K2 = the second dissociation constant for carbonic acid.
• Kc = the solubility product constant for calcium carbonate.

TDS values were found according to the USSL.

TDS = EC × 640

(12)

The standard deviation (SD) for all values of soil chemical and physical properties and groundwater chemical properties was determined.

2.4. Data Analysis and Classification

Groundwater quality was classified according to the USSL standards [26], which group waters into salinity and sodicity classes (C1–C4, S1–S4). Crop salt tolerance was assessed following [27] (

Table 1. Salt tolerance capacity of crops according to Todd’s [27] classification.

Crop Division	Electric Conductivity (EC)
	Low Salt Tolerance Crops	Medium Salt Tolerance Crops	High Salt Tolerance
Fruit Crops	(0–3000) (μS cm−1): Limon, Peach, Pear Apricot, Orange, Apple	(3000–4000) (μS cm−1): Cantaloupe, Olive, Figs, Pomegranate	(4000–10,000) (μS cm−1): Date palm
Vegetable Crops	(3000–4000) (μS cm−1): Green beans, Celery, Radish	(4000–10,000) (μS cm−1): Cucumber, Peas, Onion, Carrot, Potatoes, Lettuce, Cauliflower, Tomato	(10,000–120,000) (μS cm−1): Spinach, beets
Field Crops	(4000–6000) (μS cm−1): Field beans	(6000–10,000) (μS cm−1): Sunflower, Corn, Rice, Flax, Sorghum	(10,000–16,000) (μS cm−1): Cotton, Sugar beet, Barley (grains)

). Soil and groundwater data were statistically summarized (minimum, maximum, mean), and seasonal fluctuations were compared with river level variations. The combined assessment was used to determine the suitability of river-adjacent groundwater for irrigation and its potential impacts on soil properties.

3. Results and Discussion

3.1. Soil Characterization

To study the available groundwater, it is necessary to identify the nature of the soil properties in which this groundwater is found in order to determine the mutual influence of soil and water. As shown in

Table 2. Chemical and physical properties of the studied soils.

Location	pH	EC	Ca	Mg	Na	K	Cl	SO4	HCO3	CO3	SAR	ESP	Sand	Silt	Clay	Texture
		ds m−1	meq L−1								(mmol L−1)½	%	gm kg−1
S1	8.32	2.22	9.32	6.21	7.15	1.23	13.21	7.51	1.60	Nil	2.57	3.99	552	316	132	SL
S2	7.12	9.41	26.97	40.25	27.52	1.34	55.46	43.92	6.20	Nil	4.75	6.43	440	317	243	L
S3	7.71	3.92	14.18	12.40	12.76	1.42	25.43	13.73	1.20	Nil	3.50	5.04	443	368	189	L
S4	7.20	8.70	38.31	13.53	37.20	1.91	49.22	23.26	7.52	Nil	7.31	9.30	602	277	121	SL
S5	7.44	3.00	6.11	10.23	11.89	1.25	20.73	8.61	2.25	Nil	4.16	5.77	436	319	245	L
S6	8.25	2.12	4.99	8.31	6.82	1.60	10.22	9.01	1.97	Nil	2.64	4.07	520	271	209	SCL
S7	7.05	10.01	33.21	29.32	42.21	2.10	59.21	40.15	3.20	Nil	7.55	9.57	524	267	209	SCL
S8	7.55	4.84	16.93	14.92	15.29	1.40	22.37	25.20	1.24	Nil	3.83	5.40	459	367	174	L
S9	7.00	11.13	34.96	41.83	32.17	1.69	70.21	41.01	1.40	Nil	5.19	6.93	638	213	149	SL
S10	7.95	2.35	9.34	6.56	6.80	0.76	6.21	13.21	1.21	Nil	2.41	3.82	541	383	76	SL
S11	7.62	3.11	12.13	8.15	10.06	1.02	19.54	10.63	1.76	Nil	3.16	4.66	509	337	154	L
S12	7.31	5.18	20.8	12.96	17.62	1.32	32.5	17.60	2.11	Nil	4.29	5.92	521	339	140	L
Max	8.32	11.13	38.31	41.83	42.21	2.1	70.21	43.92	7.52	Nil	7.55	9.57	638	383	245	-
Min	7.00	2.12	4.99	6.21	6.80	0.76	6.21	7.51	1.20	Nil	2.41	3.82	436	213	76	-
Mean	7.54	5.50	18.94	17.06	18.96	1.43	32.03	21.15	2.64	Nil	4.28	5.91	515	315	170	-
SD	0.45	3.37	11.76	12.75	12.57	0.55	21.23	13.57	2.07	Nil	1.71	1.91	64.03	49.82	51.04

, soil pH values ranged between 7.00 and 8.32, with an average of 7.54, placing the soil within the neutral to slightly alkaline range. This can be attributed to the high content of limestone rocks in Iraqi soils, which are mostly calcareous [28], with calcium carbonate contents ranging from 6 to 50% [29], combined with their low organic matter content. The scarcity of rain limits natural leaching, and irrigation water in the region is typically alkaline, further contributing to alkalinity [30].

EC values of the soils varied considerably, from 2.12 to 11.13 ds m⁻¹, with an average of 5.55 ds m⁻¹. This variation among sites may reflect differences in physical and chemical properties, land use (e.g., green spaces versus agricultural plots), and management practices [31,32]. Land use across the study sites varied according to local management practices. Some locations were cultivated continuously for green spaces or field crops, while others alternated between cultivation and fallow periods depending on seasonal irrigation availability and land management objectives. Unused areas generally showed higher EC values, consistent with reduced leaching and salt accumulation [33]. Regarding cations, calcium concentrations exceeded magnesium in most samples, with mean values of 18.94 and 17.06 meq L⁻¹, respectively. This reflects the dominance of calcium carbonate in the parental material [34,35], as sedimentary deposits in Iraq are rich in calcium carbonate and gypsum. Calcium salts are also more soluble than magnesium salts, explaining their greater mobility in soil solutions, while the arid climate reduces leaching and promotes lime accumulation. In addition, irrigation water typically contains more calcium than magnesium [36].

Mean sodium concentrations (18.96 meq L⁻¹) were similar to calcium, while potassium was much lower (1.43 meq L⁻¹). The sequence of cation abundance was Na > Ca > Mg > K, although calcium values were higher than sodium values at eight out of twelve sites, reflecting the dominance of calcium-rich parent materials and the limited solubility of magnesium- and potassium-bearing minerals [37,38]

Soil SAR values ranged from 2.41 to 7.55, with an average of 4.28 (mmol L⁻¹)^½, and ESP values ranged from 3.82 to 9.57%, averaging 5.91%. All values were below the 15% sodicity threshold [39], confirming that soils are not sodic.

This is mainly due to the abundance of calcium carbonate and gypsum, which continuously supply soluble calcium that replaces sodium on the cation exchange complex, preventing sodification [40]. The relatively permeable soil texture also facilitates the leaching of soluble sodium salts, thereby limiting their accumulation. The anion composition followed the order Cl⁻ > SO₄²⁻ > HCO₃⁻, with average concentrations of 32.03, 21.15, and 2.64 meq L⁻¹, respectively. This reflects the arid climate, which restricts leaching and favors the accumulation of easily soluble chloride salts [41]. Gypsum dissolution accounts for sulfate being the second dominant ion, while bicarbonate is the least abundant due to the low solubility of calcium and magnesium carbonates [42]. These values indicate that the chloride-type salinity predominates, which is relatively easy to leach if appropriate management is applied [43].

According to the soil texture classification of the United States Department of Agriculture (USDA), three soil texture classes were identified: loam (50% of samples), sandy loam (30%), and sandy clay loam (20%). Most soils are therefore light-textured, characteristic of river shoulder deposits in central and southern Iraq [28]. These soils formed from relatively coarse sediments deposited near riverbanks during floods, while finer particles such as clay and fine silt were carried further downstream [35]. This depositional process explains the dominance of medium to light textures with high drainage capacity [44].

The relevance of soil texture lies in its influence on irrigation water suitability. Coarser soils are generally more tolerant of saline irrigation water, as leaching is facilitated, reducing salt accumulation in the root zone [45].

Overall, the soils of the study area are slightly alkaline, moderately saline, rich in calcium carbonate, and dominated by light textures with good drainage capacity. These characteristics reduce the risk of sodicity despite elevated sodium concentrations and suggest that soils can accommodate the use of moderately saline groundwater, provided that appropriate management practices such as leaching and crop selection are applied.

The close relationship between groundwater chemistry and soil characteristics in the study area underscores their mutual influence on irrigation suitability. The presence of calcium- and magnesium-rich groundwater contributes to maintaining favorable soil structure by offsetting sodium accumulation and preventing dispersion, as reflected in the low SAR and ESP values of the soils. Conversely, areas with higher groundwater salinity (as observed near W1 and W2) show moderately elevated soil EC, suggesting that periodic irrigation with more saline water promotes partial salt buildup in the upper soil layers. However, the dominance of light-textured soils with good drainage capacity facilitates leaching of soluble salts and prevents long-term sodification. In semi-arid conditions, this process is limited and may only occur during periods of higher irrigation or occasional rainfall. These results confirm that the interaction between hydrochemical composition and soil physical properties determines the sustainability of groundwater use for irrigation. Effective management, therefore, requires considering both groundwater quality and soil texture to maintain productive and non-saline conditions in river-adjacent agricultural lands.

It should be noted, however, that in semi-arid environments such as the study area, the direct geochemical interaction between groundwater, typically located at depths of 3 to 5 m, and the surface soil layer (0–30 cm) is likely to be limited. Restricted rainfall and low infiltration rates reduce vertical connectivity, meaning that similarities between soil and groundwater chemistry may reflect broader hydrogeological or lithological controls rather than direct exchange. Although this study qualitatively compares patterns in both media, no statistical correlation analysis was performed. Future investigations should include sampling of deeper soil horizons closer to the water table or assess surface water–soil interactions to better quantify these relationships.

3.2. Groundwater Characterization

The pH values of well water, ranging from 7.00 to 8.18, with an average of 7.39, are shown in

Table 3. Chemical properties of groundwater.

Location		pH	EC	Ca	Mg	Na	K	Cl	SO4	HCO3	CO3	SAR
			ds m−1	meq L−1								(mmol L−1)½
Season 1	W1	7.31	2.88	9.10	6.30	12.10	0.90	17.5	10.49	2.11	Nil	4.36
	W2	7.56	3.28	8.42	5.36	16.41	0.87	20.32	8.97	2.74	Nil	6.25
	W3	7.78	1.38	4.21	3.12	4.82	0.64	6.44	5.31	2.23	Nil	2.52
	W4	7.18	4.28	11.42	10.97	15.73	1.04	22.31	14.36	3.64	Nil	4.70
Season 2	W1	7.84	3.72	8.84	8.28	9.21	0.64	12.93	11.52	3.31	Nil	3.15
	W2	7.31	4.13	13.02	8.18	18.65	0.98	29.51	10.09	3.12	Nil	5.73
	W3	8.09	1.50	4.97	3.83	4.92	0.80	6.35	5.96	2.91	Nil	2.35
	W4	7.15	4.02	11.31	10.21	17.21	1.00	22.73	14.68	3.79	Nil	5.25
Season 3	W1	7.16	4.94	10.21	9.02	28.60	0.75	32.12	15.18	4.44	Nil	9.22
	W2	7.10	5.49	15.24	10.52	29.66	0.20	26.84	25.54	2.98	Nil	8.26
	W3	8.18	2.19	7.43	6.35	7.79	0.35	10.11	9.26	2.91	Nil	2.97
	W4	7.09	5.14	14.37	8.32	28.2	0.19	26.18	23.69	2.93	Nil	8.37
Season 4	W1	7.21	5.02	19.89	15.32	14.23	0.13	32.21	15.64	3.41	Nil	3.39
	W2	7.08	5.18	19.16	17.41	14.81	0.14	27.27	22.83	2.31	Nil	3.46
	W3	7.83	2.23	8.21	7.13	7.03	0.24	11.32	9.05	2.02	Nil	2.54
	W4	7.15	4.99	17.82	12.27	18.47	0.14	23.56	24.19	3.29	Nil	4.76
Season 5	W1	7.11	4.91	20.23	18.64	10.79	0.14	19.63	27.63	4.12	Nil	2.45
	W2	7.21	5.21	22.52	16.83	12.58	0.17	18.38	28.24	4.71	Nil	2.84
	W3	7.82	1.53	5.19	4.12	5.83	0.31	5.96	6.26	2.63	Nil	2.70
	W4	7.01	4.96	18.76	17.41	13.15	0.16	28.16	20.62	1.53	Nil	3.09
Season 6	W1	7.18	4.79	17.24	14.93	15.70	0.25	24.36	20.14	2.51	Nil	3.91
	W2	7.00	5.35	15.27	12.85	24.44	0.19	31.14	21.11	1.21	Nil	6.52
	W3	7.88	1.93	7.85	6.23	5.31	0.23	8.31	12.03	1.10	Nil	2.00
	W4	7.03	4.93	15.36	13.96	19.83	0.18	29.13	20.14	2.12	Nil	5.18
Max		8.18	5.49	22.52	18.64	29.66	1.04	32.21	28.24	4.71	Nil	9.22
Min		7.00	1.38	4.12	3.12	4.82	0.13	5.96	5.31	1.10	Nil	2.00
Mean		7.39	3.92	12.75	10.32	14.81	0.42	20.53	15.96	2.84	Nil	4.42
SD		1.55	1.41	5.39	4.72	7.48	0.33	8.78	7.19	0.93	Nil	2.07

(average values—Table 3—were calculated based on all sampling seasons). These values fall within the slightly to moderately alkaline range, reflecting the alkaline character of Iraqi soils, which are rich in calcium carbonate minerals. The surface water sources originating from the neighboring countries also derive from rocks of alkaline origin, further contributing to the alkalinity of groundwater in the region [46]. Variation in pH values among wells may be related to differences in the chemical and mineral composition of the surrounding soils, the concentration and type of dissolved salts, and surface soil management near each well [47].

EC values ranged between 1.38 and 5.49 ds m⁻¹, with an average of 3.92 ds m⁻¹. Variability between wells is partly explained by their distance from the Tigris River, as groundwater near the river tends to be more diluted [48]. Other contributing factors include soil characteristics in the vicinity of each well, land-use practices, and the degree of well exploitation [49]. Seasonal fluctuations were also observed in EC values, with higher salinity recorded in the third and fourth sampling seasons. These changes are consistent with seasonal groundwater level variations: when water levels drop, salts accumulate through upward capillary movement and dissolution from the soil matrix, while recharge from rainfall or irrigation contributes to dilution [50]. In addition, groundwater originates from multiple sources, including seepage from the Tigris River, percolation of rainfall and irrigation water, and lateral inflow from adjacent areas [51]. The Kut Dam, which regulates river levels, further influences groundwater dynamics: when the river stage is lowered, groundwater from the opposite bank may flow toward the well, often carrying higher salinity. The average calcium concentration in groundwater (12.75 meq L⁻¹) was higher than that of magnesium (10.32 meq L⁻¹). This dominance is attributed to the parent materials, which are rich in calcium carbonate and gypsum. Calcium salts are more soluble and abundant than magnesium salts, and the chemical weathering of calcium carbonates is generally more active [52]. Furthermore, dissolution, precipitation, and ion exchange processes within soil layers contribute to maintaining higher calcium levels relative to magnesium [53].

Sodium (Na⁻¹) concentrations ranged between 4.82 and 29.66 meq L⁻¹, with an average of 14.81 meq L⁻¹. The SAR values varied from 2.00 to 9.22, averaging 4.42 (mmol L⁻¹) ^½. The relatively low SAR values are linked to river recharge, which reduces sodium accumulation, and to the presence of calcium carbonate and gypsum in geological layers, which increases calcium concentrations and helps maintain cation balance [54]. According to the USSL classification, SAR values between 0 and 10 indicate low sodium hazard, corresponding to class S1, suitable for irrigation on all soil types with minimal risk of sodicity [55]. Potassium concentrations ranged between 0.13 and 1.04 meq L⁻¹, with a mean of 0.42 meq L⁻¹, showing variation between wells and seasons. This variability may be due to differences in the geological composition of aquifer materials, adsorption and release from clay minerals [56], and agricultural practices such as potassium fertilization in some areas but not others [57]. Seasonal rainfall and irrigation can also contribute to the leaching of potassium into groundwater, while groundwater level fluctuations affect its mobility and concentration [58].

Among the anions, chloride (Cl⁻¹) was dominant (20.53 meq L⁻¹), followed by sulfate (15.96 meq L⁻¹) and bicarbonate (2.84 meq L⁻¹). The prevalence of chloride is due to its high solubility and low tendency to precipitate, while sulfate derives from the dissolution of gypsum [59]. Bicarbonate is lowest, as it originates mainly from calcium and magnesium carbonates, which are relatively stable and sparingly soluble [60]. This ionic distribution indicates a chloride-type salinity phase, in which soluble chloride salts dominate. Such salts are generally easy to leach, especially sodium and calcium chloride, which are highly soluble [61].

Overall, groundwater in the study area is slightly alkaline, moderately to highly saline, dominated by calcium and sodium among cations, and chloride among anions. Its classification as S1 in terms of sodium hazard suggests that it can be safely used for irrigation across soil types, though its salinity level necessitates careful management practices, particularly during dry seasons when concentration increases.

3.3. Groundwater Levels in the Wells of the Study Sites

Figure 3 shows that groundwater levels varied across seasons and wells, reflecting both spatial and temporal fluctuations in the aquifer system. The shallowest groundwater depths were recorded in the fifth season (January 2023), with levels of 4.16, 4.11, 3.17, and 3.32 m below the soil surface for wells W1, W2, W3, and W4, respectively. By contrast, the deepest groundwater levels were observed in the third and fourth seasons, reaching 6.18, 5.98, 3.54, and 3.62 m, respectively. On average, groundwater levels across all seasons were 5.07 m in W1, 4.94 m in W2, 3.38 m in W3, and 3.44 m in W4.

The variation in well depths can be attributed to hydrogeological and topographical differences across the study area. Proximity to recharge sources such as the Tigris River, irrigation canals, and rainfall infiltration strongly influences groundwater levels [62]. Aquifer lithology also plays a significant role, as coarse-textured sediments allow for more rapid recharge and drainage, while finer textures reduce hydraulic conductivity and slow groundwater movement. In addition, wells located further from the river or at slightly elevated topography positions tend to have deeper groundwater due to weaker recharge potential [63]. In general, the river shoulder deposits within the alluvial plain are characterized by considerable heterogeneity, including differences in the composition and thickness of their layers, variations in soil texture, and fluctuations in surface elevation. In the study area, the ground surface ranges between approximately 20 and 22 m a.s.l.

Human activities also contribute to spatial variation in groundwater levels. Differences in land management, intensity of irrigation, and direct abstraction for agriculture or domestic use can locally depress groundwater levels [64]. These anthropogenic influences compound the natural variability imposed by hydrogeological conditions.

Seasonal fluctuations in groundwater levels were evident, though the pattern differed from typical expectations. In many arid and semi-arid regions, groundwater levels decline most during summer and autumn [65]. However, in the present study, the maximum declines occurred in the third and fourth seasons, while the highest rises were recorded in the fifth season. This anomaly is closely linked to the hydrological regime of the Tigris River. Controlled regulation of river discharge by the Kut Dam, particularly storage of water in upstream reservoirs during harvest periods, leads to temporary declines in groundwater levels in the study area, as reduced river stage lowers hydraulic heads and induces lateral flow of more saline groundwater from the opposite bank [66,67].

Conversely, during the fifth season, higher river discharge and the cessation of large-scale irrigation promoted groundwater recharge, resulting in shallower water levels. This pattern highlights the hydraulic connectivity between the Tigris River and adjacent aquifers, confirming that river stage fluctuations are a primary control on local groundwater availability.

Proximity to the river remains a dominant factor controlling well recharge, as demonstrated by the consistently shallower levels in wells W3 and W4, which are closest to the river. This observation reinforces the importance of considering river–aquifer interactions in managing water resources in the region, particularly in the context of seasonal irrigation demands and upstream regulation [62].

During the monitoring of the Tigris River’s water levels, there was a complete correlation between the changes in water levels in the Tigris River and the well water levels during the study period. The changes in the water levels of the Tigris River are controlled by the Iraqi Ministry of Water Resources. Therefore, during the first and second phases of the study, there were no fluctuations in the water level of the Tigris River. These phases coincided with the beginning of the agricultural irrigation season, which necessitates the Ministry of Water Resources maintaining the river levels and supplying the Tigris with stored water. However, in the third and fourth phases of the study, there was a significant decrease in water levels, despite they were during the winter season, which is characterized by rainfall, low evaporation, and a reduced need for irrigation. This decrease is attributed to the Ministry of Water Resources’ role in lowering the water level in the river due to the reduced need for water on the land, storing it in reservoirs for use during periods of water scarcity.

The results of the groundwater characterization of well water (Table 3), when correlated with fluctuations in groundwater levels, showed that these fluctuations affect the EC of the well water. Specifically, the salinity of the water increased as the groundwater level decreased. Furthermore, variations in EC were observed between wells based on their distance from the Tigris River, with groundwater closer to the river generally being less saline. These findings clearly demonstrate the significant role of fluctuations in the Tigris River’s water levels in influencing the quality of groundwater in wells.

It is important to note that the groundwater found in wells adjacent to the Tigris River is hydraulically connected to the river itself and does not represent an independent or additional water source. The observed fluctuations in groundwater levels in the four analyzed wells largely reflect variations in river stage, indicating that a significant portion of the water extracted from these wells originates as induced infiltration from the river channel. Therefore, groundwater abstraction in such settings should be managed carefully to avoid excessive drawdown, which could alter hydraulic gradients and reduce river discharge, particularly during dry seasons or low-flow conditions. This process, known as streamflow depletion by groundwater pumping, has been widely documented in hydrogeological studies (e.g., [68,69,70]). Recognizing this hydraulic interdependence emphasizes the need for integrated surface–groundwater management to ensure the sustainability of both river and aquifer systems.

3.4. Groundwater Quality

The theoretical pH (pHc) calculated using the Langelier equation ranged from 5.4 to 6.4, with an average of 5.9 (

Table 4. Quality of groundwater and its suitability for irrigation.

Location		PHc	TDS	SI	RSC	SARadj	Na%	SR	JR	PS	MR
			mg L−1	-	meq L−1	(mmol L−1)½	%	-	-	meq L−1	%
Season 1	W1	6.1	1843.20	1.21	−13.29	14.39	47.27	8.29	0.69	22.75	40.91
	W2	6.0	2099.20	1.56	−11.04	21.25	55.63	7.42	0.81	24.81	38.90
	W3	6.4	883.20	1.38	−5.10	7.56	42.69	2.89	0.75	9.10	42.56
	W4	5.8	2739.20	1.38	−18.75	16.92	42.82	6.13	0.71	29.49	49.00
Season 2	W1	5.9	2380.80	1.94	−13.81	11.03	36.52	3.91	0.71	18.69	48.36
	W2	5.9	2643.20	1.41	−18.08	20.06	48.08	9.46	0.63	34.56	38.58
	W3	6.2	960.00	1.89	−5.89	7.52	39.39	2.18	0.77	9.33	43.52
	W4	5.8	2572.80	1.35	−17.73	18.90	45.83	6.00	0.76	30.07	47.44
Season 3	W1	5.8	3161.60	1.36	−14.79	33.19	60.42	7.23	0.89	39.71	46.91
	W2	5.7	3513.60	1.40	−22.78	30.56	53.69	9.01	1.11	39.61	40.84
	W3	5.9	1401.60	2.28	−10.87	10.40	37.14	3.47	0.77	14.74	46.08
	W4	5.9	3289.60	1.19	−19.76	29.30	55.58	8.94	1.08	38.03	36.67
Season 4	W1	5.7	3212.80	1.51	−31.80	12.54	28.97	9.45	0.44	40.03	43.51
	W2	5.8	3315.20	1.28	−34.26	12.46	29.02	11.81	0.54	38.69	47.61
	W3	6.1	1427.20	1.73	−13.32	8.38	32.15	5.60	0.62	15.85	46.48
	W4	5.7	3193.60	1.45	−26.80	17.61	38.21	7.16	0.78	35.66	40.78
Season 5	W1	5.5	3142.40	1.61	−34.75	9.56	21.95	4.76	0.55	33.45	47.95
	W2	5.4	3334.40	1.81	−34.64	11.36	24.47	3.90	0.68	32.50	42.77
	W3	6.2	979.20	1.62	−6.68	8.64	39.74	2.27	0.98	9.09	44.25
	W4	6.0	3174.40	1.01	−34.64	10.51	26.90	18.41	0.47	38.47	48.13
Season 6	W1	5.8	3065.60	1.38	−29.66	14.08	33.15	9.71	0.64	34.43	46.41
	W2	6.1	3424.00	0.90	−26.91	21.52	46.69	25.74	0.78	41.70	45.70
	W3	6.4	1235.20	1.48	−12.98	6.00	28.24	7.55	0.64	14.33	44.25
	W4	5.9	3155.20	1.13	−27.20	18.13	40.56	13.74	0.68	39.20	47.61
Min		5.4	883.20	0.90	−34.75	6.00	21.95	2.18	0.44	9.09	36.67
Max		6.4	3513.6	2.28	−5.10	33.19	60.42	25.74	1.11	41.70	49.00
Mean		5.9	2506.13	1.48	−20.23	15.49	39.90	8.13	0.73	28.51	44.38

). The saturation index (SI) values varied between 0.90 and 2.28, averaging 1.48. All values of SI were positive, indicating that the groundwater is oversaturated with respect to calcium carbonate and therefore has the potential to precipitate carbonates upon contact with soil or under evaporation conditions [36].

TDS concentrations ranged from 883.2 to 3513.6 mg L⁻¹, with a mean of 2506.13 mg L⁻¹. According to the USSL classification [20], groundwater from wells W1, W2, and W4 fell within the very high salinity class (1500–3000 mg L⁻¹), while water from W3 consistently fell within the high salinity class (500–1500 mg L⁻¹). Such water is unsuitable for irrigation under normal conditions but may be used for controlled circumstances, specifically in highly permeable soils with efficient drainage and when cultivating salt-tolerant crops. The observed differences in water quality between wells are related to variations in the lithology of aquifer materials, proximity to recharge sources, and intensity of local groundwater exploitation [32].

Adjusted SAR values ranged from 6.0 to 33.19 (mmol L⁻¹)^½, with an average of 15.49 (mmol L⁻¹)^½. RSC values were consistently negative, ranging from −34.75 to −5.10 meq L⁻¹ (mean −20.23 meq L⁻¹), indicating suitability for irrigation [71]. Negative RSC values reflect the dominance of calcium and magnesium over carbonate and bicarbonate, which reduces the risk of soil alkalinization. PS, an indicator of chloride hazard based on Doneen’s [14] method, ranged from 9.09 to 41.70 meq L⁻¹, with a mean of 28.51 meq L⁻¹. Values for W1, W2, and W4 in all seasons exceeded 15, placing them in the poor category, whereas W3 recorded lower PS values (9.09–15.85 meq L⁻¹), falling into the medium category [72].

Na% values ranged from 21.95 to 60.42%, with an average of 39.90%. All values were below 60% except in W1 during the third season, confirming, according to Wilcox’s classification [24], that the sodium hazard is generally within acceptable limits for irrigation [36]. MR values ranged from 36.67% to 49.00%, averaging 44.38%. Since none exceeded the critical threshold of 50%, the groundwater is considered suitable for irrigation in terms of magnesium hazard [73].

There are five categories according to the SR: good quality (<0.5), slightly contaminated (0.5–1.3), moderately contaminated (1.3–2.8), injuriously contaminated (2.8–6.6), and highly contaminated (6.6–15.5), according to Lekshmi and Kani [74]. SR values ranged from 2.18 to 25.74, with a mean of 8.13. According to the SR categories, groundwater in the study area was classified as moderately contaminated (8.3%), injuriously contaminated (37.3%), and highly contaminated (58.3%). These high SR values suggest substantial external contributions of saline water, which may be linked to lateral inflows or anthropogenic contamination [75].

JR values ranged from 0.44 to 1.11, averaging 0.73. Approximately 83.3% of samples had values below 0.86, indicating the influence of saltwater intrusion, while 8.3% exceeded 1.00, suggesting contamination from other saline or wastewater sources [76,77]. This may also be a result of the impact of drainage water from agricultural lands adjacent to the study area, particularly when these drains have reduced drainage efficiency. Furthermore, the main drainage catchment for the drainage networks in the alluvial plain is located approximately 30 km from the study area and ultimately empties into the sea.

PS value (meq L⁻¹) for irrigation water indicates the severity of chloride and its impact on soil permeability. Doneen’s classification [14] establishes three water quality classifications: (i) good water quality, with PS values less than 7 for highly permeable soils, less than 5 for medium permeability, and less than 3 for low permeability; (ii) medium water quality, with PS values ranging from 7 to 15 for high permeability, 5–10 for medium permeability, and 3–5 for low permeability; (iii) poor water quality, with PS values greater than 15 for high permeability, greater than 10 for medium permeability, and greater than 5 for low permeability. Table 4 shows PS values ranged from 9.09 to 41.70 meq L⁻¹, averaging 28.51 meq L⁻¹. Values for W1, W2, and W4 in all seasons exceeded 15 meq L⁻¹, placing them in the poor category, whereas W3 recorded lower PS values (9.09–15.85 meq L⁻¹), falling into the medium category [78]. PS classification confirms that most groundwater samples fall into the poor category, except for W3 in seasons 1, 2, and 5, which were classified as medium. This reinforces the need for soil permeability considerations in irrigation planning, as chloride-rich water can impair soil structure and reduce infiltration capacity.

The relationship between groundwater depth and salinity was also examined. The shallowest depth recorded was 3.28 m (W4), which is greater than the 2.5 m critical threshold for upward capillary rise [58]. Thus, groundwater in the study area is unlikely to contribute to soil salinization through capillary action. Moreover, the generally coarser soil textures further reduce the risk of salinity migration from groundwater to the root zone [79]. According to the USSL diagram [20], groundwater from W1, W2, and W4 falls into the C4S1 class (very high salinity, low sodium), while W3 is classified as C3S1 (high salinity, low sodium) (Figure 4). This means that although the sodium hazard is low, the high salinity severely restricts its use for irrigation unless special management practices are applied. Such practices include blending with fresher water, ensuring efficient drainage, and selecting salt.

Comparison with Todd’s classification [27] (Table 1), crop tolerance classification shows that groundwater in the study area could support medium- and high-salinity-tolerant crops, provided leaching requirements are observed. Examples include barley, cotton, sugar beet, and certain forage grasses, while sensitive crops would be at significant risk.

In summary, groundwater quality in the study area is characterized by high to very high salinity, low sodium hazard, and variable contamination signatures. While not generally suitable for unrestricted irrigation, it can be used under carefully managed conditions, particularly in coarse-textured soils with efficient drainage systems and when cultivating salt-tolerant crops.

The outcomes of this study suggest several approaches for managing groundwater resources in arid and semi-arid environments, such as those surrounding the Tigris River. Wells located close to riverbanks should be prioritized for irrigation use, since they tend to yield groundwater of better quality due to direct recharge from river water. At the same time, regular monitoring of groundwater depth and salinity is essential to track changes arising from seasonal river fluctuations, irrigation intensity, and long-term exploitation. Such tracking would allow early detection of risks and the adjustment of management practices accordingly.

Crop selection is another key consideration. Because most of the groundwater analyzed falls within the high to very high salinity range, cultivation should focus on salt-tolerant species such as barley, cotton, sugar beet, or certain forage grasses, while avoiding sensitive crops that would perform poorly under these conditions. To prevent salt accumulation in the root zone, irrigation should be combined with leaching requirements, supported by well-designed drainage systems that can remove excess salts effectively.

In addition, the conjunctive use of water sources can enhance sustainability. Mixing groundwater with fresher water supplies or alternating between fresh and saline water during irrigation cycles can reduce salinity stress on crops and improve water-use efficiency. Care must also be taken to avoid excessive exploitation of wells adjacent to rivers, since this may accelerate lateral seepage and lower groundwater levels, threatening the long-term stability of both the aquifer and the river system.

By adopting these integrated practices (combining careful well placement, systematic monitoring, crop and soil management, and balanced water use), groundwater of marginal quality can become a reliable supplementary source for agriculture. Such measures are particularly important in the context of increasing water scarcity, where sustainable strategies are required to safeguard both agricultural productivity and soil health. Sustainability cannot be achieved through excessive use of irrigation water, as this leads to soil degradation and disruption of the quantity and quality of groundwater in the region.

3.5. Limitations and Future Investigations

Although groundwater in the study area has been exploited for more than a decade, no evident adverse effects have been observed; continuous monitoring remains essential. Long-term irrigation with moderately to highly saline groundwater can lead to cumulative impacts that may only become evident over extended timeframes. Thus, periodic assessments of groundwater depth and quality are necessary to detect emerging risks and guide adaptive management strategies. Another important consideration is the role of the well location relative to the Tigris River. While proximity to the river often enhances groundwater quality through dilution, distance alone does not uniformly predict water suitability. The influence of hydrogeological factors, particularly the composition and permeability of aquifer layers, can override distance effects. Future investigations should therefore aim to establish scientifically validated thresholds for well placement along riverbanks, accounting for both lithological variability and hydrodynamic conditions. The utilization of groundwater from wells adjacent to rivers presents opportunities but also significant challenges. On one hand, such wells capture water that naturally seeps from the river, potentially providing a renewable source of irrigation water. On the other hand, excessive reliance on this mechanism could accelerate lateral seepage, lower regional groundwater levels, and destabilize the balance between river discharge and aquifer recharge. This, in turn, could reduce the availability of groundwater for agriculture and diminish the ecological functions of river–aquifer interactions.

While the findings of this study demonstrate that groundwater in river-adjacent wells can be used as an auxiliary source for irrigation under specific conditions, its utilization must be approached with caution. The high to very high salinity levels observed in some wells, coupled with the hydraulic connection between the river and the aquifer, imply that uncontrolled abstraction may lead to increased soil salinity, reduced river baseflow, and degradation of riparian ecosystems. Therefore, these resources should not be viewed as an independent or supplementary water supply but rather as part of an integrated river–aquifer system that requires balanced management. Future strategies should focus on regulating pumping rates, monitoring water quality trends, and applying soil–water management practices that minimize ecological and hydrological risks while maintaining agricultural productivity.

Future research should therefore focus on integrated water resource management strategies that balance groundwater extraction with river recharge dynamics. Such studies should also evaluate the cumulative impacts of continued groundwater use on soil health, the effectiveness of blending or alternating groundwater with fresher water sources, and the economic feasibility of cultivating salt-tolerant crops under these conditions.

4. Conclusions

The results of this study demonstrate that fluctuations in freshwater levels in the Tigris River appear to influence the quality of adjacent groundwater. Fluctuating freshwater levels in rivers, together with the influence of local soil and water management practices and human activity, are likely to contribute to the observed spatial and temporal variability in groundwater salinity and chemical composition. This variability may reflect the influence of lateral movement of more saline groundwater, as suggested by the spatial distribution of salinity values and supporting geochemical indicators such as the Jones Ratio (JR). This shows the impact of different feeding sources, represented by groundwater movements towards the study area and other sources such as water seeping from neighboring areas and drains in agricultural lands near the study area.

Despite these challenges, groundwater from wells near the river represents a valuable resource for agriculture in arid and semi-arid regions facing severe water scarcity. Such wells are commonly located in coarse-textured soils, as documented in previous studies of riverbank deposits across central Iraq, and this observation aligns with the light-textured soils identified in the present study area. Under such conditions, and according to established irrigation water quality classifications, moderately saline groundwater can be used for irrigation in coarse-textured soils without causing significant long-term soil degradation, especially when suitable management practices such as leaching and crop selection are applied. This aligns with local irrigation practices, where water of similar salinity is already used for crop production.

However, sustainable utilization of this resource requires careful management. Appropriate practices include the selection of salt-tolerant crops, implementation of leaching requirements, and, where possible, blending with fresher water to mitigate salinity risks. These strategies can ensure that groundwater remains a reliable supplementary water source while safeguarding soil health and agricultural productivity.

In conclusion, the study highlights the importance of integrated river–aquifer management in water-scarce environments. By aligning groundwater extraction with hydrological dynamics and adopting adaptive soil and crop management practices, groundwater near rivers can continue to play a vital role in sustaining agriculture under conditions of increasing water scarcity. The use of this groundwater for irrigation must be approached with caution to avoid overexploiting the river’s water resources for the sustainability of groundwater use in the study area.