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Article

Watershed-Scale Benefits of Using Reclaimed Water for Agricultural Irrigation

by
Emma L. Gray
,
Azbina Rahman
,
Masoud Negahban-Azar
,
Paul T. Leisnham
and
Adel Shirmohammadi
*
Department of Environmental Science and Technology, University of Maryland, College Park, MD 20742, USA
*
Author to whom correspondence should be addressed.
Water 2026, 18(5), 615; https://doi.org/10.3390/w18050615
Submission received: 22 January 2026 / Revised: 27 February 2026 / Accepted: 28 February 2026 / Published: 4 March 2026
(This article belongs to the Special Issue Sustainable and Efficient Water Use in the Face of Climate Change)
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Abstract

Agricultural irrigation is increasing due to climate stress and yield benefits on crops in the Mid-Atlantic region. To lessen groundwater demand, reclaimed water has grown as a popular freshwater alternative for irrigation. While reclaimed water (treated wastewater from wastewater treatment plants (WWTPs)) provides many benefits, additional costs deter farmers from its adoption. This study assesses the economic feasibility of reclaimed water for agricultural irrigation in two Mid-Atlantic watersheds: the Zekiah watershed in southern Maryland and the Greensboro watershed in eastern Maryland and southwestern Delaware. We identified areas most feasible for reclaimed water irrigation based on WWTP capacity, unit prices for water, and yield benefits of irrigation under diverse precipitation scenarios for both watersheds. Under dry precipitation conditions and a unit cost of $0.10 per cubic meter of reclaimed water (m3), 29.77% of cropland in the Zekiah watershed and 34.32% of cropland in the Greensboro watershed are feasible for reclaimed water irrigation, conserving a potential 1,505,154.72 m3 and 12,381,703.45 m3 of freshwater, respectively. However, when reclaimed water pricing and precipitation increase, significantly fewer farms experience sufficient yield benefits to cover reclaimed water costs. Further adoption of reclaimed water irrigation could be enhanced by a cost-share program that covers costs when yield benefits cannot.

1. Introduction

Global agriculture is highly susceptible to climate change impacts due to more variable temperatures and precipitation. By the end of the century, total crop yield losses are projected to reach 11% [1], further threatening food security and economic well-being worldwide. One adaptive strategy to combat crop loss and meet increasing food demands under climate stress is the use and expansion of supplemental irrigation. Irrigated agriculture can significantly boost crop yields when compared with rain-fed agriculture, especially in arid regions [2,3,4].
However, while supplemental irrigation increases the productivity and resilience of agriculture and food systems, irrigation already consumes a substantial portion of freshwater within the United States. Irrigation comprised an estimated 42% of all freshwater withdrawals within the U.S. in 2015 [5], with the overwhelming majority of freshwater being sourced from groundwater aquifers [6]. In the Mid-Atlantic region, deep groundwater in confined aquifers declined 1.36 m (m) (4.46 feet; ft) from 2002 to 2016, with 88% of cultivated areas experiencing groundwater decline in highly agricultural areas [7]. Excessive groundwater withdrawal can result in irreversible environmental impacts such as saltwater intrusion, land subsidence, reduced flow, and reduced storage capacity of aquifers. Threatened groundwater reliability can force farmers to pursue more costly water supply options, challenging farmers’ economic well-being. To preserve critical freshwater resources and foster resilience within water systems, the implementation of more efficient and sustainable irrigation best management practices in agriculture is crucial [8,9,10,11,12].
Reclaimed water reuse is one emerging management practice to supplement water demand in irrigation. Reclaimed water, also referred to as recycled water or alternative water, is treated wastewater from wastewater treatment plants (WWTPs) and can be used directly for irrigation when advanced water treatment is applied. By reusing reclaimed water for irrigation, farms can reduce freshwater withdrawals, increase water use efficiency with additional nutrient input [13], foster water supply reliability to meet crop water demand, and improve crop productivity [14]. Additionally, by reusing reclaimed water, a circular economy perspective can be adopted, where water resources are recycled, promoting more conscious, efficient water use [15,16,17].
Despite the benefits of reclaimed water irrigation, currently only 2–15% of all treated wastewater is reused for irrigation globally [18]. One of the largest barriers to reclaimed water implementation in agriculture is the cost associated with reclaimed water, including advanced treatment processes, infrastructure installation, operation, and maintenance [19,20,21,22]. Additionally, while groundwater use is free in most states across the U.S. after well and irrigation infrastructure costs, reclaimed water requires a unit cost per volume to ensure water quality and reliability, hindering the desirability of reclaimed water use. This additional cost can reduce the cost-recovery associated with supplemental irrigation and may introduce economic disparity among farms of different sizes and financial capacities [3,19,23]. Effective regulation, management, and equitable distribution of reclaimed water are therefore essential in implementing sustainable alternative water resources and reducing disparity within agriculture.
In Maryland (MD), irrigation practices have steadily increased. From 1956 to 2007, irrigated cropland increased an estimated 730%, from 4521 hectares (ha) (11,174 acres; ac) to 37,556 ha (92,805 ac). Of this area, less than 1% was irrigated with reclaimed water in 2018 [24]. Despite this, the majority of WWTPs in the state employ advanced wastewater treatment technologies to limit excess nutrient loading into the Chesapeake Bay when discharged into surface waters. Wastewater treated with advanced filtration and disinfection within MD is classified as Class IV reclaimed water and is already approved for activities with higher human contact potential, including agricultural irrigation for food crops that are commercially processed and non-food crops [25]. While most regions struggle with regulatory barriers to implement reclaimed water irrigation, only economic and infrastructural barriers pose a threat to reclaimed water adoption in Maryland.
To overcome these barriers, the net benefit value approach can be applied to propose that economic benefits provided by agricultural irrigation can eliminate cost barriers associated with reclaimed water use when net profits are greater than zero [26]. Within the U.S., few studies have been conducted on farm feasibility based on net profit and cost-recovery associated with reclaimed water irrigation. Economic analyses of reclaimed water use have been conducted for plant nurseries in southern New Jersey [27], plant nurseries in southern California [28], and within urban settings in Austin, Texas [29]. Cost recovery analyses have also been recreated for similar irrigation schemes, such as tailwater recovery systems in Mississippi and irrigation technology adoption in MD [30,31]. Other suitability analyses for reclaimed water use, such as land suitability for Maryland [32], farmers’ perceptions and attitudes for the Mid-Atlantic region [33], and farmers’ perceptions and attitudes nationally [34], have been considered for the U.S. However, watershed-scale analyses of reclaimed water economics are few and far between. Outside of the U.S., reclaimed water research has been further developed, and farmers’ willingness to pay has been investigated for Greece [35,36], Iran [37], Spain [38], Jordan [39], Ghana [40], Bangladesh [41], China [26], and Italy [42]. Cost analyses including non-market benefits of reclaimed water have been developed for Australia [43], Spain [44], Tunisia [21], and China [26].
To our knowledge, no study has leveraged empirically derived crop water requirements in a market-only cost–benefit analysis of reclaimed water for crop use in the Mid-Atlantic region. Thus, this study aims to develop a cost-benefit analysis for reclaimed water irrigation adoption by isolating potential yield benefits, reclaimed water unit costs, and water conveyance costs for two Mid-Atlantic watersheds. Through a watershed-scale approach, supplemental irrigation crop water demands and yields were achieved using the Soil and Water Assessment Tool (SWAT) model by considering soil conditions and land use [45]. Resulting SWAT model outputs were then applied to individual farm parcels within both watersheds to evaluate economic gain from additional yield, cost for supplemental reclaimed water, and subsequent economic feasibility for reclaimed water use. This cost-benefit analysis can be utilized to determine the quantity of fresh groundwater preserved with the use of reclaimed water for irrigation and identify the farms most feasible for reclaimed water use under varied unit costs of reclaimed water and climate scenarios. In areas limited by treated wastewater capacity, this cost-benefit analysis can also help prioritize farms with optimized net benefits from irrigation and minimized distances from a WWTP.

2. Materials and Methods

2.1. Study Area

This study considers two watersheds within Maryland (MD) and Delaware (DE): the Zekiah and Greensboro watersheds (Figure 1). Both watersheds are located within the Coastal Aquifer System in the Coastal Plain physiographic region and drain into the Chesapeake Bay.
The Zekiah watershed is in southern MD and contained within Charles, Prince George’s, and St. Mary’s Counties, MD [47]. This watershed has freshwater-use competition between municipal consumption and farm irrigation, and land use in the Zekiah watershed is predominantly forest (58%), developed land (16%), agriculture (13%), and wetlands (11.5%) (Figure 1). Within the 28,900.00 ha (71,413.45 acres; ac) of the Zekiah watershed, there are 689.50 ha (1703.79 ac) of corn production and 869.50 ha (2148.58 ac) of soybean production [48] (Figure 2). According to the U.S. Census Bureau [49], Charles County’s 2020 population density was 140.50 people per square kilometer (km2) (363.90 people per square mile; mi2) [49].
In contrast, the Greensboro watershed is situated in Caroline and Queen Anne’s Counties, MD, and Kent County, DE [50], with land use distributed as forested (10%), developed (5%), wetland (30%), and agriculture (55%). Of Greensboro watershed’s total area of 38,900.00 ha (96,123.99 ac), 5223.00 ha (12,906.31 ac) produce corn and 5720.00 ha (14,134.43 ac) produce soybeans (Figure 2). Queen Anne’s County’s 2020 population density was 51.81 people per km2 (134.20 people per mi2) [51]. Compared with the Zekiah watershed, the Greensboro watershed is more intensely agricultural but experiences less freshwater use competition. Because of this, the Greensboro watershed was selected to represent a traditional agricultural area containing larger farm parcels, while the Zekiah watershed was selected to represent a residential area containing small agricultural parcels. The contrasting land use and freshwater dynamics between these two watersheds are key to the analysis of this study.
In the Mid-Atlantic region, crops are primarily irrigated by on-farm groundwater wells using drip, center pivot, and travelling gun irrigation systems [52]. Within both the Zekiah and Greensboro watersheds, agriculture is dominated by soybean and corn crops irrigated primarily by on-farm groundwater wells using center pivot and travelling gun irrigation systems [53]. Both corn and soybean crops are ideal for reclaimed water use as they fall under MD’s Class IV reclaimed water approved list as major non-food crops and crops that are commercially processed [25].
Within MD, Class IV reclaimed water must meet the following water quality standards: a monthly average biochemical oxygen demand of 10 milligrams (mg) per liter (L), a daily average turbidity of 2 Nephelometric Turbidity Units, a monthly median E. coli concentration of 1.0 Most Probable Number (MPN) per 100 milliliters (mL), a monthly median fecal coliform concentration of 2.2 MPN/100 mL, a pH range of 6.5–8.5 standard units, a monthly average total nitrogen concentration of 10 mg/L, total residual chlorine concentrations of 1.5–4.0 mg/L at the treatment outlet, and total residual chlorine concentrations of 0.4–4.0 mg/L at the sampling locations [25].

2.2. Data Collection and Processing

2.2.1. Crop Data

Agricultural parcel boundary information for this study was collected for both Maryland and Delaware from the best available data [54,55]. Soybean and corn cropland cover maps were collected from the Cropland Data Layer (CDL) raster dataset [48]. Parcel boundary data was then overlaid on top of CDL data to extract parcels where cropland was located and calculate corn and soybean acreage by individual farm.

2.2.2. Wastewater Treatment Plant Data

Wastewater treatment plant (WWTP) data for publicly owned facilities was collected for both the Zekiah and the Greensboro watershed regions [56]. Municipal WWTPs were prioritized based on larger capacities and closest proximities to agricultural parcels within the watersheds. Then, buffer zones around the primary WWTPs were created based on WWTP annual capacity and farm water demand in the region (Figure 3). Farms were then assigned a WWTP based on the proximity from the centroid of the farm parcel to the WWTP.
For the Zekiah watershed, two WWTPs were considered for the final analysis. The largest WWTP in this region is the La Plata WWTP, located in the western portion of the watershed with an annual capacity of 1,453,598.13 cubic meters (m3) (384.00 million gallons; Mgal), and the second prioritized WWTP in the Zekiah watershed is the Clifton on the Potomac WWTP, located south of the watershed with an annual capacity of 55,267.01 m3 (14.60 Mgal) (Table 1). An 8 km (4.97 mi) radius buffer area was employed for the La Plata WWTP, and a 10 km (6.21 mi) radius buffer area was employed for the Clifton on the Potomac WWTP. These buffer areas were established to avoid overlap between WWTPs, maximize reclaimed water potential in this watershed, and minimize piping distance. In areas where WWTPs overlapped, larger WWTPs with greater capacities were prioritized for a farm’s irrigation needs. Buffer areas established within the Zekiah watershed contain 36.13% of all soybean area and 43.74% of all corn area within the watershed.
For the Greensboro watershed, three WWTPs were included in the final analysis (Figure 3). The primary WWTP in this region is the Kent WWTP, located east of the watershed in DE, with an annual capacity of 16,330,872.17 m3 (4314.10 Mgal). The other WWTPs considered are the Denton WWTP, located south of the watershed with an annual capacity of 671,532.05 m3 (177.40 Mgal), and the Sudlersville WWTP, located northwest of the watershed with an annual capacity of 99,242.14 m3 (26.20 Mgal) (Table 1). A 25 km (15.53 mi) buffer area was established for the Kent WWTP, and 20 km (12.42 mi) buffer areas were established for both the Denton and Sudlersville WWTPs (Figure 3). Buffer areas established for the Greensboro watershed contain 100% of all soybean and corn area within the watershed.

2.2.3. Crop Yield and Irrigation Water Demand Data

The Soil and Water Assessment Tool (SWAT) hydrologic model was developed and calibrated for both the Zekiah and Greensboro watersheds to determine ideal supplemental irrigation requirements and crop yields for irrigated and rainfed fields [45,57]. SWAT models simulate hydrologic dynamics within a watershed considering unique soil and geology classifications, elevation, land use classifications, and climate data [58,59]. Through watershed subbasin characteristics, SWAT models can produce highly detailed spatial crop yields and irrigation needs by crop type, subbasin area, and climate. Because SWAT is a physical model, the tool provides a unique yet crucial perspective into agricultural water management [45].
Model calibration and validation for both watersheds were conducted by Rahman et al. [45] and Zhang et al. [57] utilizing the SWAT model’s Calibration and Uncertainty modules (SWAT-CUP) with the sequential uncertainties fitting version 2 (SUFI-2) algorithm for optimizing calibration. The SWAT models were calibrated with default SWAT streamflow parameters for 1998–2007 and validated from 2008 to 2015 (Table 2), and the models’ crop yield predictive performances were evaluated for both rainfed and irrigated fields (Table 3). Evaluation metrics used include the coefficient of determination (R2), Nash-Sutcliffe model efficiency (NSE) coefficient, Kling-Gupta efficiency (KGE) coefficient, and root mean square error (RMSE). R2 values indicate collinearity between observed and predicted values, where a value of one indicates a perfect fit between observed and predicted. NSE values range from negative infinity to one, where a negative value indicates that the observed values are better than model simulation output and a value of one indicates that the model predicts observed values perfectly. Similarly, KGE ranges from negative infinity to one, where a value of one indicates high model accuracy. RMSE values indicate the average difference between model values and observed values, with lower values signifying better model performance. For further information on model parameters and evaluation, see Rahman et al. [45].
The SWAT models were run under three precipitation scenarios: a wet precipitation scenario, a dry precipitation scenario, and an average precipitation scenario for the growing season (May through September) within Maryland. These scenarios were selected as extreme seasonal precipitation that occurred between 1980 and 2016, based on best available precipitation and crop yield data for MD. The wet scenario had 887.00 mm (34.92 in) of precipitation (2003), the average scenario had 662.00 mm (26.06 in) of precipitation (2009), and the dry scenario had 277.00 mm (10.90 in) of precipitation during the growing season (2007; Figure 4) [60]. Additionally, 2003’s growing season had an average minimum and maximum temperature ranging from 52 to 86 degrees Fahrenheit (°F), 2007’s growing season had an average minimum and maximum temperature ranging from 54 to 88 °F, and 2009’s growing season had an average minimum and maximum temperature ranging from 53 to 87 °F [60].

2.3. Economic Analysis

Within this study, a threshold-price perspective is employed rather than a full life-cycle cost analysis for costs associated with reclaimed water. Because of this, the main barriers for farms considering reclaimed water for irrigation are economic cost, including conveyance and unit price per volume, and reclaimed water availability based on regional WWTP capacity. All piping infrastructure was assumed to be present and was thus not included within the economic analysis to limit uncertainty. Additionally, while water storage infrastructure such as tanks and ponds can be utilized to optimize reclaimed water capacity and reduce freshwater reliance during drier precipitation years, our analysis considered only the direct application of reclaimed water from WWTPs and did not introduce secondary storage at farms. For conveyance cost, due to the high variability of conveyance costs with topography, an estimated cost per distance was assumed to be fixed across all WWTPs. Determination of reclaimed water cost per volume is discussed further in Section Farm Economic Suitability.
To select farm parcels most feasible for reclaimed water irrigation for corn and soybean crops, an Ultimate Economic Benefit (UEB), determined by the Net Benefit from Irrigation (NBI), unit cost of reclaimed water (RWC), and conveyance costs based on distance to transport reclaimed water, was calculated (Figure 5). Farms that had positive UEB and capacity at their assigned WWTPs were considered most feasible and selected to receive reclaimed water. Farms that had negative UEB, or positive UEB but no water capacity at their WWTP, were not feasible. This analysis was inspired by the IrrigEcon decision support system framework and the geospatial multi-criteria decision analysis framework conducted by Hanna et al. and Paul et al. [30,32].

Farm Economic Suitability

Supplemental water requirements for irrigation, baseline crop yields, and target crop yields for soybean and corn area were derived from the SWAT model outlined by Rahman et al. [45]. Crop yield improvements from supplemental irrigation were calculated as the difference between baseline crop yields ( Y L D c ) and total yields with supplemental irrigation applied (Yt,c). Then, economic benefit from irrigation by corn and soybean area for each farm ( B I , c , f ) was calculated using crop area ( A c , f ) and sale price of crop yield (Ps,c) in the following adapted equation [30,61]:
B I , c , f = Y t , c − Y L D c × A c , f ∗ P s , c
where,
  • B I , c , f = Benefit from irrigation by crop c for farm f ($)
  • Yt,c = Target yield with supplemental irrigation for crop c (kg/ha)
  • Y L D c = Harvested yield without supplemental irrigation for crop c (kg/ha)
  • A c , f = Area of crop c for farm f (ha)
  • Ps,c = Sale price of yield for crop c ($/kilogram)
Reclaimed water cost was determined by the unit cost of reclaimed water ( R W c ) and the total volume of water required for each crop acreage per farm ( V o l I ). Net economic gain from irrigation for each farm ( N B I , f ) in both watersheds was then calculated as the difference between combined profit from irrigation and reclaimed water cost for each farm in the following equation:
N B I , f = B I ,   C o r n ,   f + B I , S o y b e a n , f − ( R W C ∗ V o l I , f )
where,
  • N B I , f = Net benefit from irrigation farm f ($)
  • B I ,   C o r n , f = Benefit from irrigation for corn area for farm f ($)
  • B I , S o y b e a n , f = Benefit from irrigation for soybean area for farm f ($)
  • R W C = Unit cost for reclaimed water ($/m3)
  • V o l I , f = Irrigation volume applied to farm f over the growing season (m3)
Unit prices for crops were set at $0.17 per kilogram (kg) ($4.40 per bushel) for corn and $0.35 per kg of soybeans ($9.75 per bushel), based on averaged Maryland grain bids across the 2024 growing season [62]. Crop market prices were kept constant between precipitation scenarios for simplicity, but it should be noted that market prices may differ upwards of $0.10–0.20 per kg depending on demand.
Cascading rates for reclaimed water costs were set to represent fixed and variable costs associated with advanced treatments required in MD to achieve Class IV reclaimed water. These costs include operational costs, treatment and disinfection, WWTP maintenance energy costs, and other WWTP operational costs for a small to medium-sized municipal WWTP. Average reclaimed water rates in the U.S. range from $0.10 to $0.50 per m3, depending on the level of water treatment, region, and water volume. For example, the Eastern Municipal Water District of Perris, California, charges $0.13 per m3 for summer irrigation, assuming customers are connected to the ‘backbone’ system [63]. For irrigators requiring more service than the ‘backbone’ system, the EMWD charges $0.42 per m3 [63]. Similarly, the City of Tucson, Arizona, charges $0.84 per m3 [64], and Austin Water of Austin, Texas charges $0.36 per m3 of recycled water [65]. Because reclaimed water rates are generally established for municipal and urban settings and larger volumes typically result in lower unit costs, reclaimed water unit costs for irrigation are assumed to be within or under these provided examples. Cascading values for the unit cost of reclaimed water were considered in the following six cost scenarios: $0.00 per m3, $0.03 per m3, $0.05 per m3, $0.10 per m3, $0.20 per m3, and $0.30 per m3. The $0.20 per m3 pricing scenario is assumed to be the standard pricing, while the $0.10 per m3 pricing and those below are assumed to be a subsidized or cost-share scenario pricing.
Conveyance cost was assumed to be a fixed cost of $0.02 per km ($37.00 per 1000 miles) [66]. This cost covers the energy required to pump reclaimed water from the WWTP to the farm and is therefore directly dependent on distance. It should be noted that conveyance cost is highly variable and does not include pipe infrastructure, excavation, repaving, and other processes involved in pipeline construction. Shorter distances between farms and WWTPs will result in lower costs for farmers and is thus more desirable. Here, an ultimate economic benefit for farm f is determined as the conveyance cost of each farm’s distance to a WWTP subtracted from the farm’s N B I , as seen in the following equation:
U l t i m a t e   E c o n o m i c   B e n e f i t f = N B I ,   f − ( $ 0.02 k m ∗ d i s t f )
where
  • U l t i m a t e   E c o n o m i c   B e n e f i t f = Total net economic benefit from reclaimed water irrigation for farm f ($)
  • d i s t f = Distance of farm f to wastewater treatment plant (km)
  • N B I , f = Net benefit from irrigation for farm f ($)
Farms were sorted in descending order of ultimate economic benefit (UEB), and farms with a value greater than or equal to zero are considered feasible and selected to receive reclaimed water, given available WWTP capacity. Farms with a UEB less than zero indicate infeasibility without additional cost-share, subsidy programs, or social benefits of alternative water resources considered. Feasible farms were selected for wet, dry, and average precipitation conditions for both watersheds using the above UEB criteria. Farms to be irrigated under $0.20 per m3 of reclaimed water, average reclaimed water pricing within the U.S., and $0.10 per m3 of reclaimed water, subsidy pricing for reclaimed water within the U.S., were visualized in ArcGIS Pro 3.3.0 [67].
Finally, threshold unit costs at which reclaimed water irrigation becomes no longer profitable were determined as the average N B I , f of farms within both watersheds under the three precipitation scenarios when no initial water cost is incorporated.

3. Results

3.1. Crop Yield and Irrigation Demand

Water requirements were determined from the SWAT model, as previously described in Rahman et al. [45] for both the Zekiah and Greensboro watersheds. For an average precipitation year in Maryland, total supplemental water requirements for irrigation were found to be 2,906,950.21 m3 (767.93 Mgal) for 1558.99 ha (3852.37 ac) of cropland in the Zekiah watershed and 20,215,590.46 m3 (5340.39 Mgal) for 10,943.81 ha (27,042.76 ac) of cropland in the Greensboro watershed (Table 4).

3.2. Zekiah Watershed Feasibility

In the Zekiah watershed, 310 farms, 615.50 ha (1520.95 ac) of cropland, were considered for reclaimed water irrigation. Using ultimate economic benefit (UEB), which considers N B I , distance to a WWTP, conveyance cost, and WWTP capacity, 69 farms can feasibly irrigate (199.89 ha) with reclaimed water when water is priced at $0.20 per m3 during the dry precipitation scenario in the Zekiah watershed. During the wet and average precipitation scenarios, no farms are considered feasible due to a lack of net benefit from irrigation. However, when water is priced at $0.03 per m3 in the Zekiah watershed, 10 farms can feasibly irrigate (2.22 ha) in the wet precipitation scenario, 74 farms can feasibly irrigate (466.82 ha) in the dry precipitation scenario, and 235 farms can irrigate (489.14 ha) in the average precipitation scenario (Figure 6). The maximum number of farms and volume of freshwater conserved are limited by the WWTP water capacities within the region. For the dry precipitation scenario, the fewest number of farms can irrigate with reclaimed water due to the sum of the total water requirement for each farm exceeding total reclaimed water capacity in the Zekiah watershed.
Under the dry precipitation year and $0.03–0.10 per m3 water pricing, a maximum of 1,505,154.72 m3 (397.62 Mgal) of fresh groundwater could be conserved utilizing reclaimed water for irrigation in the Zekiah watershed (Figure 7). This volume of water is limited by regional WWTP capacity (Table 5), rather than UEB, and decreases towards zero m3 as the cost of reclaimed water increases to $0.10 per m3 in the average precipitation scenario and $0.30 per m3 in the dry scenario.
Utilizing the $0.10 per m3 reclaimed water subsidy cost in the Zekiah watershed, an estimated 29.77% of cropland was selected for reclaimed water irrigation under the dry scenario. Selected agricultural land decreases to 12.72% utilizing the $0.20 per m3 pricing under dry conditions in the Zekiah watershed (Figure 8).
Given the average net benefit of farms within the Zekiah watershed, the threshold price for reclaimed water was determined to be $0.17 per m3 under the dry precipitation scenario (Table 4). This represents the highest price that farms could afford before reclaimed water becomes economically infeasible within the Zekiah watershed.

3.3. Greensboro Watershed Feasibility

In the Greensboro watershed, 3677 farms, 9358.09 ha (23,124.36 ac) of cropland, were considered for reclaimed water use. When considering UEB and a $0.20 per m3 reclaimed water pricing under the dry precipitation scenario, no farm can afford reclaimed water irrigation (Figure 9). The number of farms selected increases to 1218 (3744.26 ha) for $0.03–0.10 per m3 of reclaimed water pricing under the dry scenario. Farms were limited most by net positive economic benefits from irrigation, and total reclaimed water capacity is never reached in the Greensboro watershed (Figure 10). All farms within the Kent WWTP buffer area can receive reclaimed water, but neither the Denton nor Sudlersville WWTP can serve more than three farms under dry conditions, even when a $0.00 per m3 unit cost per reclaimed water volume is assigned, due to limited annual reclaimed water capacity.
Under the $0.10 per m3 of reclaimed water pricing, 1218 farms (3744.26 ha) were selected for reclaimed water irrigation under dry precipitation conditions (Figure 11). This indicates the number of farms that had positive UEB values from irrigation and desirable distance from a WWTP under projected subsidized pricing of reclaimed water. Overall, 3744.26 ha (9252.27 ac), or 34.32%, of cropland are selected for reclaimed water irrigation under subsidized pricing.
Threshold pricing at which benefits from irrigation no longer cover reclaimed water cost was found to be $0.16 per m3 under the dry precipitation scenario (Table 4). This represents the highest price that farms could afford before reclaimed water would become economically infeasible in the Greensboro watershed.

4. Discussion

As shown in this study, the use of reclaimed water for supplemental irrigation for corn and soybean in Maryland is feasible under dry and average precipitation conditions for reclaimed water costs of $0.03–0.10 per m3 of reclaimed water. Once pricing increases to $0.20 per m3, only under dry precipitation conditions do farms have a sufficient net benefit from irrigation to feasibly utilize reclaimed water for irrigation.
Within the U.S., these costs are most like prices within California, where regular prices are $0.20–0.30 per m3 of treated water and discounted prices are considered 50% reductions of this price, $0.10 per m3 [68,69]. Given the economic data of this study, irrigating corn and soybean with reclaimed water under wet and average precipitation conditions without reduced unit costs remains unprofitable for farmers in Zekiah and Greensboro watersheds. As corroborated by Rahman et al. [45] and Hanna et al. [30], regional WWTPs in the Zekiah watershed have sufficient water capacity to serve all considered farms under the wet precipitation scenario, but our results show that supplemental economic return on crop yields remains insufficient for a reclaimed water price of $0.20 or $0.30 per m3. In contrast, while the Greensboro watershed has sufficient reclaimed water available, profits from irrigation are not sufficient to cover unit costs and conveyance costs associated with reclaimed water irrigation. The difference in limitations between watersheds highlights the need for watershed-specific feasibility studies. Future considerations for the Greensboro watershed could include a centralized pumping center to decrease the overall distance and conveyance cost that farmers must incur to utilize reclaimed water. In the Zekiah watershed, considerations could increase annual capacities at regional WWTPs or on-farm storage tanks to avoid WWTP capacity-related competition amongst farms. A tiered-cost system for unit cost of reclaimed water by water demand and capacities could also improve the equitable adoption of reclaimed water in diverse climate and demographic areas [9,16]. A tiered system would vary reclaimed water unit costs depending on the total volume of reclaimed water drawn for farm irrigation. Additional economic support could be provided to farms that do not currently experience sufficient benefit from irrigation to cover reclaimed water costs.
For both watersheds, the highest unit cost for reclaimed water that farmers could feasibly pay to achieve net positive irrigation benefits is $0.17 per m3 of reclaimed water and occurs during the dry precipitation year. Our results suggest that the net benefit of production with irrigation increases compared with rainfed production, balancing out higher unit costs for water. This is corroborated by Brennan et al., who identified a feasible unit cost of $0.36 per m3 of reclaimed water for arid regions like Queensland, Australia [43]. This threshold is almost double what farmers within the Zekiah or Greensboro watershed could feasibly afford and reflects that under future climate scenarios, reclaimed water irrigation is likely to become more economically feasible to farmers as yield benefits from irrigation increase.
Considering that agricultural irrigation is heavily influenced by cost in both water use and irrigation system selection [30,70], financial incentives and external benefits of reclaimed water should be investigated to determine freshwater management strategies. Institutional coordination, social awareness, and best management practices have been modeled to support greater use of reclaimed water [19], combating negative outcomes associated with cost recovery. Other impactful improvements to modeling reclaimed water adoption include the introduction of socioeconomic factors that drive farmer decision-making, such as sustainability knowledge, awareness of reclaimed water benefits, and social stigma concerns. Future work should consider farmer attitudes, infrastructural feasibility, and institutional support to better facilitate the integration of reclaimed water irrigation.
As groundwater levels continue to decline in the Mid-Atlantic region, a unit cost may be imposed upon groundwater withdrawal. Because of this, the actualized price of reclaimed water will decrease relative to groundwater unit costs. For example, if groundwater is priced at $0.05 per m3, the baseline cost of supplemental irrigation for farmers decreases to an actualized $0.15 per m3 of reclaimed water in contrast to its face value of $0.20 per m3 of reclaimed water. Consequently, reclaimed water will also emerge as a more feasible option when water resources become more threatened.
This study uniquely analyzes the reclaimed water irrigation feasibility by isolating the cost recovery associated with supplemental irrigation costs and yield benefits. This allows economic barriers of reclaimed water to be evaluated without the coupled external and social benefits associated with reclaimed water. When economic returns are greatest in drier seasons, reclaimed water emerges as a feasible alternative to groundwater withdrawals to improve crop yields and economic well-being in Maryland agriculture. Further, the proposed framework of prioritizing farms with the greatest economic returns for more costly water best management practices mitigates the potential for growing economic disparity among farmers as climate shifts force farmers to invest in more costly management strategies. While this study cannot fully encapsulate the potential adoption of reclaimed water without social acceptance, infrastructural feasibility, and institutional support present, results from this work will inform an agent-based model that integrates socioeconomic and infrastructural factors to simulate the adoption of reclaimed water irrigation [71].

5. Conclusions

In this study, a threshold-price economic analysis is conducted to explore the impact of reclaimed water irrigation yield benefits on cost recovery from reclaimed water unit pricing and conveyance costs. Under dry precipitation conditions and subsidized pricing, this framework could provide reclaimed water to 1218 farms in the Greensboro watershed and 74 farms in the Zekiah watershed, conserving 12,382,013.45 m3 (3270.98 Mgal) and 1,505,162.72 m3 (397.621 Mgal) of freshwater in the declining confined aquifer systems per growing season. However, financial cost and distance from a WWTP remain a huge barrier to reclaimed water feasibility among farms within the Mid-Atlantic region of the U.S. For a more thorough analysis, socioeconomic dynamics, groundwater resource availability, institutional support, and infrastructural feasibility should be integrated to simulate willingness and complex economic dynamics of agricultural irrigation systems.
This watershed-shed analysis isolates limiting factors and threshold costs at which farmers can feasibly afford reclaimed water to maximize fresh groundwater resources in the Mid-Atlantic region. To further the equitable distribution of alternative water resources, this framework can be applied to prioritize farms that will experience the greatest net economic returns and minimal distance from WWTPs. As precipitation becomes more variable and distributed non-uniformly during the growing season in the Mid-Atlantic region, this framework can also be used to plan financially for lower profit years to offset reclaimed water costs and support the longevity of freshwater resources. This ensures equitable water resource use even in years when benefits from reclaimed irrigation cannot cover the costs associated with irrigation practices.

Author Contributions

Conceptualization, M.N.-A., A.S.; methodology, E.L.G., A.R., M.N.-A., A.S.; software, A.R.; validation, A.R.; formal analysis, E.L.G., A.R.; investigation, E.L.G.; data curation, E.L.G., A.R.; writing—original draft preparation, E.L.G.; writing—review and editing, E.L.G., A.R., M.N.-A., A.S.; visualization, E.L.G., A.R.; supervision, M.N.-A., A.S., P.T.L.; project administration, M.N.-A., A.S., P.T.L.; funding acquisition, M.N.-A., A.S. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the USDA National Institute of Food and Agriculture (USDA-NIFA), grant number 1027960.

Data Availability Statement

The raw data supporting the conclusions of this article will be made available by the authors on request.

Conflicts of Interest

The authors declare no conflicts of interest.

Abbreviations

The following abbreviations are used in this manuscript:
CDLCrop Data Layer
NBNet Benefit
SWATSoil and Water Assessment Tool
UEBUltimate Economic Benefit
WWTPWastewater Treatment Plant

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Figure 1. Location and land use for the Zekiah watershed in Maryland (left) and the Greensboro watershed located across two states, Maryland and Delaware (right) [46].
Figure 1. Location and land use for the Zekiah watershed in Maryland (left) and the Greensboro watershed located across two states, Maryland and Delaware (right) [46].
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Figure 2. (a) Corn and soybean acreage in the Zekiah watershed in Charles’ County, MD; (b) Corn and soybean acreage in the Greensboro watershed in Queen Anne’s and Caroline Counties, MD, and Kent County, DE. Parcels are outlined in black, with areas shaded in black indicating higher density parcels in residential areas.
Figure 2. (a) Corn and soybean acreage in the Zekiah watershed in Charles’ County, MD; (b) Corn and soybean acreage in the Greensboro watershed in Queen Anne’s and Caroline Counties, MD, and Kent County, DE. Parcels are outlined in black, with areas shaded in black indicating higher density parcels in residential areas.
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Figure 3. Major municipal wastewater treatment plants (WWTPs) and annual capacities in cubic meters (m3) near the: (a) Zekiah watershed; (b) Greensboro watershed. Parcels are outlined in black, with areas shaded in black indicating higher density parcels in residential areas.
Figure 3. Major municipal wastewater treatment plants (WWTPs) and annual capacities in cubic meters (m3) near the: (a) Zekiah watershed; (b) Greensboro watershed. Parcels are outlined in black, with areas shaded in black indicating higher density parcels in residential areas.
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Figure 4. Maryland precipitation (millimeters; mm) during the growing season for 2003 (orange), 2007 (yellow), and 2009 (grey) to represent wet, dry, and average precipitation scenarios. Horizontal lines shown in the same respective colors reflect precipitation averages for the growing season (May–September) by year [45]. Horizontal lines display seasonal average precipitation values for the wet, average, and dry precipitation scenario.
Figure 4. Maryland precipitation (millimeters; mm) during the growing season for 2003 (orange), 2007 (yellow), and 2009 (grey) to represent wet, dry, and average precipitation scenarios. Horizontal lines shown in the same respective colors reflect precipitation averages for the growing season (May–September) by year [45]. Horizontal lines display seasonal average precipitation values for the wet, average, and dry precipitation scenario.
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Figure 5. Framework for selecting most feasible farms for reclaimed water irrigation considering yield benefits from irrigation, reclaimed water unit costs per volume, conveyance costs, and regional wastewater treatment plant (WWTP) capacities.
Figure 5. Framework for selecting most feasible farms for reclaimed water irrigation considering yield benefits from irrigation, reclaimed water unit costs per volume, conveyance costs, and regional wastewater treatment plant (WWTP) capacities.
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Figure 6. The number of farms selected to irrigate under precipitation scenarios and reclaimed water costs in dollars per cubic meter ($/m3) in the Zekiah watershed. The wet precipitation year is depicted in orange, the dry year in yellow, and the average year in grey.
Figure 6. The number of farms selected to irrigate under precipitation scenarios and reclaimed water costs in dollars per cubic meter ($/m3) in the Zekiah watershed. The wet precipitation year is depicted in orange, the dry year in yellow, and the average year in grey.
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Figure 7. The volume of freshwater conserved in cubic meters (m3) with the proposed use of reclaimed water irrigation under growing season precipitation and cost scenarios in dollars per cubic meter ($/m3) in the Zekiah Watershed. The wet precipitation year is depicted in orange, the dry year in yellow, and the average year in grey.
Figure 7. The volume of freshwater conserved in cubic meters (m3) with the proposed use of reclaimed water irrigation under growing season precipitation and cost scenarios in dollars per cubic meter ($/m3) in the Zekiah Watershed. The wet precipitation year is depicted in orange, the dry year in yellow, and the average year in grey.
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Figure 8. For the Zekiah watershed, farms depicted in blue are feasible for reclaimed water irrigation given: (a) $0.10 per cubic meter (m3); (b) $0.20 per m3 under the dry precipitation scenario. Both consider WWTP distance, net economic profit, and WWTP capacity. Parcels are outlined in black, with areas shaded in black indicating higher density parcels in residential areas.
Figure 8. For the Zekiah watershed, farms depicted in blue are feasible for reclaimed water irrigation given: (a) $0.10 per cubic meter (m3); (b) $0.20 per m3 under the dry precipitation scenario. Both consider WWTP distance, net economic profit, and WWTP capacity. Parcels are outlined in black, with areas shaded in black indicating higher density parcels in residential areas.
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Figure 9. Number of farms irrigated under growing season precipitation scenarios and reclaimed water unit costs per volume in dollars per cubic meter ($/m3) for the Greensboro watershed. The wet precipitation year is depicted in orange, the dry year in yellow, and the average year in grey.
Figure 9. Number of farms irrigated under growing season precipitation scenarios and reclaimed water unit costs per volume in dollars per cubic meter ($/m3) for the Greensboro watershed. The wet precipitation year is depicted in orange, the dry year in yellow, and the average year in grey.
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Figure 10. Volume of freshwater conserved in cubic meters (m3) when selected farms irrigate by growing season precipitation and unit cost per volume scenarios in dollars per cubic meter ($/m3) for the Greensboro watershed. The wet precipitation year is depicted in orange, the dry year in yellow, and the average year in grey.
Figure 10. Volume of freshwater conserved in cubic meters (m3) when selected farms irrigate by growing season precipitation and unit cost per volume scenarios in dollars per cubic meter ($/m3) for the Greensboro watershed. The wet precipitation year is depicted in orange, the dry year in yellow, and the average year in grey.
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Figure 11. For the Greensboro watershed, farms depicted in blue are selected for reclaimed water irrigation given: (a) $0.10 per cubic meter (m3); (b) $0.20 per m3 under the dry precipitation scenario. Both consider WWTP distance, net economic profit, and WWTP capacity. Parcels are outlined in black, with areas shaded in black indicating higher density parcels in residential areas.
Figure 11. For the Greensboro watershed, farms depicted in blue are selected for reclaimed water irrigation given: (a) $0.10 per cubic meter (m3); (b) $0.20 per m3 under the dry precipitation scenario. Both consider WWTP distance, net economic profit, and WWTP capacity. Parcels are outlined in black, with areas shaded in black indicating higher density parcels in residential areas.
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Table 1. Wastewater Treatment Plants (WWTPs) and their annual discharge flows in the Study Area.
Table 1. Wastewater Treatment Plants (WWTPs) and their annual discharge flows in the Study Area.
WatershedWWTPBuffer Size (km)Annual Capacity (m3/yr)
ZekiahLa Plata81,453,598.13
Clifton on the Potomac1055,267.01
GreensboroKent2516,330,872.17
Denton20671,532.05
Sudlersville2099,242.14
Table 2. SWAT model calibration and validation performance for streamflow in Zekiah and Greensboro watersheds. Validation values are shown in parentheses. Adapted from Rahman et al. [45].
Table 2. SWAT model calibration and validation performance for streamflow in Zekiah and Greensboro watersheds. Validation values are shown in parentheses. Adapted from Rahman et al. [45].
WatershedR2 (Validation)NSE (Validation)KGE (Validation)
Zekiah0.84 (0.63)0.84 (0.61)0.91 (0.63)
Greensboro0.62 (0.63)0.62 (0.61)0.66 (0.63)
Table 3. SWAT model predictive performance evaluation for rainfed and irrigated crop yields in the Zekiah and Greensboro watersheds. Adapted from Rahman et al. [45].
Table 3. SWAT model predictive performance evaluation for rainfed and irrigated crop yields in the Zekiah and Greensboro watersheds. Adapted from Rahman et al. [45].
WatershedTypeNSE Rainfed (Irrigated)RMSE Rainfed (Irrigated) (kg/ha)
ZekiahCorn0.67 (0.6)1382.75 (2445.46)
Soybean0.62 (−0.03)573.93 (587.92)
GreensboroCorn−5.2 (−0.17)3962.04 (1717.79)
Soybean−2.94 (−0.33)961.74 (559.52)
Table 4. Total Supplemental Irrigation Requirements (m3) for the Zekiah and Greensboro Watersheds by precipitation scenarios and crop type.
Table 4. Total Supplemental Irrigation Requirements (m3) for the Zekiah and Greensboro Watersheds by precipitation scenarios and crop type.
WatershedCrop TypeDry Year (m3) *Wet Year (m3) *Average Year (m3) *
ZekiahCorn2,322,917.95548,089.771,096,671.65
Soybean2,995,169.231,086,148.201,810,259.63
GreensboroCorn17,588,991.634,150,211.938,300,423.87
Soybean22,754,141.677,149,090.8711,915,151.45
Note(s): * These scenarios were based on precipitation from 2003, 2007, and 2009, where the wet precipitation scenario had 887.000 mm (mm) of precipitation (2003), the average precipitation scenario had 662.00 mm of precipitation (2009), and the dry precipitation scenario had 277.00 mm of precipitation during the growing season (2007).
Table 5. Threshold cost of reclaimed water per volume ($/m3) that farmers can afford in the Zekiah and Greensboro watersheds under wet, dry, and average precipitation scenarios.
Table 5. Threshold cost of reclaimed water per volume ($/m3) that farmers can afford in the Zekiah and Greensboro watersheds under wet, dry, and average precipitation scenarios.
Highest Feasible Unit Cost Per Volume of Reclaimed WaterWet ($/m3)Dry ($/m3)Average ($/m3)
Zekiah Watershed0.010.170.07
Greensboro Watershed0.010.160.07
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MDPI and ACS Style

Gray, E.L.; Rahman, A.; Negahban-Azar, M.; Leisnham, P.T.; Shirmohammadi, A. Watershed-Scale Benefits of Using Reclaimed Water for Agricultural Irrigation. Water 2026, 18, 615. https://doi.org/10.3390/w18050615

AMA Style

Gray EL, Rahman A, Negahban-Azar M, Leisnham PT, Shirmohammadi A. Watershed-Scale Benefits of Using Reclaimed Water for Agricultural Irrigation. Water. 2026; 18(5):615. https://doi.org/10.3390/w18050615

Chicago/Turabian Style

Gray, Emma L., Azbina Rahman, Masoud Negahban-Azar, Paul T. Leisnham, and Adel Shirmohammadi. 2026. "Watershed-Scale Benefits of Using Reclaimed Water for Agricultural Irrigation" Water 18, no. 5: 615. https://doi.org/10.3390/w18050615

APA Style

Gray, E. L., Rahman, A., Negahban-Azar, M., Leisnham, P. T., & Shirmohammadi, A. (2026). Watershed-Scale Benefits of Using Reclaimed Water for Agricultural Irrigation. Water, 18(5), 615. https://doi.org/10.3390/w18050615

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