Abstract
Extracted peatlands experience strong hydrological fluctuations due to drainage, vegetation succession, and climatic variability, yet long-term, high-frequency groundwater data remain scarce in Northern Europe. Our dataset presents two years (June 2023–May 2025) of 30-min groundwater table depth (WTD) measurements from six wells installed across contrasting Greenhouse Gass Emission Site Types (GEST 5, 6, 15, 20) in the Kaigu peatlands, central Latvia. Each well was equipped with an automatic pressure transducer (TD-Diver, van Essen Instruments) recording absolute pressure (m H2O). The dataset also includes metadata on coordinates, installation elevation, well construction, and manual control measurements. All values are unprocessed, i.e., they represent original logger outputs without atmospheric or elevation correction, enabling users to apply their own calibration or referencing methods. This is the first openly available high-frequency extracted peatland groundwater pressure dataset from the Baltic region and provides a foundation for hydrological modelling and rewetting designs.
Dataset:https://data.mendeley.com/datasets/n4p64ffv73/1, accessed on 9 October 2025.
Dataset License: CC BY 4.0
1. Summary
Peatlands are highly sensitive to water-table dynamics that control decomposition rates, vegetation composition, and greenhouse gas emissions. After industrial peat extraction ceases, water regimes become unstable due to altered drainage and surface topography. Baseline hydrological data are therefore crucial for planning rewetting or paludiculture activities. The Kaigu peatland, located in central Latvia, represents a typical cut-over peatland area with strong microtopographic variation and fluctuating groundwater levels. Although hydrological modelling of Baltic peatlands has advanced, raw groundwater pressure data from extracted sites are rarely, if ever, available for open use.
In 2023, a monitoring network was established across a 16.4-ha section of Kaigu peatland to collect continuous groundwater table depth and barometric pressure data representing major surface and vegetation types defined by the Greenhouse Gas Emission Site Type approach. The recorded parameters capture both short-term variability and long-term seasonal changes in peatland water regimes.
2. Data Description
2.1. Dataset Overview
The dataset is distributed as an Excel file containing three sheets:
- (1)
- Info—a brief description of dataset content and variable definitions, including details on the structure of data fields and units in the monitoring records.
- (2)
- KaiguPeatlandWaterMonitoring—the primary worksheet containing raw pressure data (in cm H2O) recorded by six TD-Diver loggers installed in groundwater wells across the Kaigu peatland. The data are organized by well, with separate columns for date, time, and recorded pressure values. Each record represents an individual 30-min measurement interval between June 2023 and May 2025.
- (3)
- KaiguPeatlandBarometerData—a complementary worksheet providing raw barometric pressure measurements from the reference logger placed in the well WTD2. These values allow users to apply their own atmospheric corrections when calculating hydraulic head or groundwater-table depth.
All datasets are unprocessed and represent original logger outputs exported directly from Diver-Office software v.12.0.3.0. []. Data are expressed in centimeters of water column (cm H2O), maintaining high temporal resolution. This structure enables full transparency and flexible reuse of the data for hydrological modelling, quality control, or comparison with other peatland sites.
2.2. Study Site
The monitoring area lies within the Kaigu peatland (56°43′ N, 23°35′ E), Jelgava district, Latvia (Figure 1). The total bog complex covers 1955 ha, of which approximately 763 ha remain in active peat extraction and 676.7 ha are designated as Natura 2000 territory. The studied 16.4 ha sector has been abandoned for several years and is undergoing spontaneous recolonization by reeds and shrubs.
Figure 1.
(A,B) Location of Kaigu peatland (orange) in Latvia and the Baltic region. Regional context showing Riga Bay and Jelgava district. (C) Detailed map of the water monitoring wells (with the LKS-92 coordinates) within the study area at Kaigu peatland.
Peat thickness ranges from 0.3 to 2.8 m, composed mainly of fen-type peat over sandy/silty substrate []. The peat deposit overlies fine-grained glaciolacustrine sands and silts that form the local groundwater aquifer. The hydraulic conductivity of the peat ranges from 1 × 10−4 to 1 × 10−6 m s−1, typical of moderately decomposed fen peat. Residual drainage ditches enhance lateral water exchange and maintain shallow groundwater connectivity. Microtopography and residual ditches create a mosaic of moisture conditions that correspond to four main Greenhouse Gas Emission Site Type (GEST) classes (GEST 5—dry bare peat surface; GEST 6—moist lawns on bare peat; GEST 15—tall reed stands (Phragmites australis); GEST 20—open water or drainage ditches). The categories capture the principal ecohydrological diversity of the site [].
2.3. Water Monitoring Wells
The groundwater monitoring well was constructed using a 50 mm PVC pipe installed through the peat layer into the underlying mineral ground (Figure 2). The upper section of the pipe is non-perforated to prevent surface water infiltration, while the lower section, located within the mineral soil, is perforated to allow groundwater entry for accurate monitoring. The bottom of the pipe was sealed with a PVC cap to prevent sediment intrusion. The upper end of the well was fitted with a protective cover to prevent contamination and enable easy access for measurement devices. A TD-Diver (van Essen) automatic datalogger was suspended inside the pipe to record groundwater level and temperature variations continuously, using the top of the casing as a fixed reference point for manual or automated measurements. WTD1 was installed in a drainage ditch to measure ditch water level.
Figure 2.
Schematic illustration of groundwater monitoring well installation (50 mm PVC pipe) through peat into mineral ground with Micro-Diver datalogger placement.
Pressure sensors were positioned within the saturated zone and programmed to record absolute pressure. A single barometric logger was installed (in water monitoring well WTD2) to enable atmospheric corrections if required. For more detail see Table 1.
Table 1.
Details of groundwater monitoring wells in Kaigu peatland.
2.4. Manual Inspection Records
In addition to continuous logging, each monitoring well was manually checked during field visits to ensure correct logger function and to verify consistency with in situ water levels. Measurements were taken from the top of the well casing using a water level meter and converted to absolute elevation (m a.s.l.) based on RTK GPS benchmarks. These periodic observations were used to confirm logger stability and to detect any potential sensor drift over time. The results of these manual checks are summarized in Table 2.
Table 2.
Summary of manual inspection data used to verify logger performance.
2.5. File Contents and Variable Description
The excel dataset is structured to provide clear metadata and direct usability for further analyses (Table 3). Each row represents a single timestamped absolute pressure observation from a given well. The dataset uses simple, self-explanatory variable names to facilitate import into R, Python, or other statistical software and environment.
Table 3.
Variables in dataset.
The dataset preserves the raw logger output without any compensation, allowing users to perform their own barometric corrections, vertical referencing, or derived estimations such as hydraulic head and water-table depth.
2.6. Data Coverage
To demonstrate the completeness of the dataset, Table 4 summarizes the temporal coverage and data continuity for each groundwater monitoring well. Continuous records span from June 2023 to May 2025, except for one logger (WTD5), which was damaged in mid-2025. Minor data gaps (<1%) occurred due to short-term instrument interruption such as data download (see dates for inspection from Table 1 to align with possible short-term disruption).
Table 4.
Temporal coverage and data completeness for groundwater level monitoring in Kaigu peatland.
3. Methods
3.1. Data Collection
Each logger recorded absolute pressure using factory calibration. Instruments were deployed in May 2023 and retrieved or downloaded at specific times (during water monitoring well inspection). The dataset includes complete records, except for WTD5, which was damaged, and sensor lost to unknown influencing factor in 2025.
3.2. Data Handling
Raw data were exported using Diver-Office software v.12.0.3.0. (van Essen instruments) and compiled into Excel format. Only minimal processing was performed: (1) formatting timestamps into local time (UTC +3); (2) removal of duplicate timestamps; (3) Annotation of short gaps (<1%) due to temporary logging interruptions (during data downloading times in a field). No atmospheric correction, head calculation, or offset adjustments are applied in the published dataset.
3.3. Data Validation
To confirm instrument accuracy, manual depth-to-water readings were taken during field visits and compared to logger pressure trends. Agreement among wells and between repeated visits verified the internal consistency of the network. The strengths of the dataset are: (1) continuous two-year record of raw pressure; (2) six monitoring points covering diverse GEST classes; (3) direct instrument outputs, enabling transparent re-use and recalculation. Limitations: (1) one logger (WTD5) lost during 2025; (2) frost-related noise possible in some winter months. Minor data gaps (<1%) and possible frost-related signal noise during winter months represent the main limitations of the dataset but do not affect overall data integrity.
4. User Notes
This dataset is best suited for users wishing to:
- (1)
- calculate corrected groundwater heads or water-table depth series using their preferred barometric and elevation references;
- (2)
- calibrate hydrological or groundwater models;
- (3)
- compare raw pressure behaviour among ecohydrological surface types;
- (4)
- evaluate responses of extracted peatlands to rewetting or natural inundation.
When converting pressure data to water-table depth or hydraulic head, users may use the general equation:
where H—hydraulic head (m a.s.l.), Pabs—absolute pressure from logger, Patm—barometric pressure (from nearby station or our provided barometric logger), and z—elevation of sensor base (m a.s.l.). In this dataset, only well-head elevations (m a.s.l.) are provided (Table 1). The exact sensor depth below the casing may vary slightly, and therefore z values are not included. Users can reference water levels to the well head or apply their own vertical offset.
Supplementary Materials
The following supporting information can be downloaded at: https://data.mendeley.com/datasets/n4p64ffv73/1.
Author Contributions
Conceptualization, N.S. and J.B.; methodology, N.S. and I.G.; field investigation, N.S. and J.B.; data curation, N.S. and J.B.; formal analysis, N.S.; visualization, N.S.; writing-original draft preparation N.S. and S.A.; writing-review and editing, J.B. and I.G.; supervision, I.G. and S.A. All authors have read and agreed to the published version of the manuscript.
Funding
This research was funded by the Latvia University of Life Sciences and Technologies doctoral project grant “Strengthening the Institutional Capacity of Latvia University of Life Sciences and Technologies for Excellence in studies and Research” (funded by the Recovery and Resilience Facility 5.2.1.1.i.0/2/24/I/CFLA/002).
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
Data is available as Supplementary Material.
Acknowledgments
The authors thank Laflora Ltd. for logistical support and the Lake and Peatland Research Centre for field assistance and data management suggestions.
Conflicts of Interest
S.A. was employed by the company Laflora Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be constructed as a potential conflict of interest.
Abbreviations
The following abbreviations are used in this manuscript:
| WTD | Water table depth |
| GEST | Greenhouse Gas Emission Site Type |
| H | Hydraulic head (m a.s.l.) |
| Pabs | Absolute pressure from logger |
| Patm | Barometric pressure (from nearby station or our provided barometric logger) |
| z | Elevation of sensor base (m a.s.l.) |
References
- Van Essen Instruments. 2016. Available online: https://www.vanessen.com/images/PDFs/Diver-ProductManual-en.pdf (accessed on 9 October 2025).
- Stivrins, N.; Bikse, J.; Jeskins, J.; Ozola, I. Hands-On Approach to Foster Paludiculture Implementation and Carbon Certification on Extracted Peatland in Latvia. Land 2024, 13, 188. [Google Scholar] [CrossRef]
- Stivrins, N.; Bikse, J.; Grinfelde, I. Groundwater Dynamics and Ecohydrological Responses in an Extracted Peatland in Central Latvia. Hydrology 2025. submitted. [Google Scholar]
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© 2025 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).