Soil-Groundwater Controls on the Hydrological Fate of Recycled-Water in a Restored Wetland
Start Date
3-16-2026 4:00 PM
End Date
3-16-2026 6:00 PM
Abstract
This study evaluates the hydrologic fate of treated wastewater (“recycled water”) used for irrigation at Thomas Dairy, a restored wetland near Tigard, Oregon, managed by Clean Water Services (CWS). We employed a water-balance framework, combining field and laboratory measurements, to assess how soil properties, groundwater depth, and atmospheric demand influenced infiltration and water availability across three soil types: Cove clay, Wapato silty clay loam, and McBee silty clay loam.
During the monitoring period (19 July–22 August 2024), total hydrologic input via irrigation and precipitation was 0.718 cm/day, with minimal precipitation. Evapotranspiration averaged 0.625 cm/day (FAO Penman-Monteith), leaving 0.094 cm/day for infiltration and storage. Soil-moisture decreased in response to atmospheric demand, particularly in shallow soils. Water-storage capacity across all soil types was driven by groundwater depth, which ranged from 15-76 cm (SSURGO database) to 5 m (CWS monitoring well). Estimated groundwater depths translated into limited storage capacity (2-14 cm) using SSURGO values, with greater storage capacity (25-30 cm) based on measured groundwater depths. Since irrigation occurs during the summer, when groundwater levels are lowest and soil-water storage capacity is highest, the estimated time required to replenish soil-water is likely to exceed a single irrigation season. This suggests that the irrigation rates as applied are unlikely to influence groundwater.
These findings underscore the importance of soil and groundwater interactions in managing recycled water, offering insights for evaluating groundwater recharge potential, optimizing irrigation, and identifying suitable sites for water reuse in future wetland restoration projects.
Subjects
Hydrology, Land/watershed management, Soil science, Sustainable development
Creative Commons License
This work is licensed under a Creative Commons Attribution-Share Alike 4.0 License.
Soil-Groundwater Controls on the Hydrological Fate of Recycled-Water in a Restored Wetland
This study evaluates the hydrologic fate of treated wastewater (“recycled water”) used for irrigation at Thomas Dairy, a restored wetland near Tigard, Oregon, managed by Clean Water Services (CWS). We employed a water-balance framework, combining field and laboratory measurements, to assess how soil properties, groundwater depth, and atmospheric demand influenced infiltration and water availability across three soil types: Cove clay, Wapato silty clay loam, and McBee silty clay loam.
During the monitoring period (19 July–22 August 2024), total hydrologic input via irrigation and precipitation was 0.718 cm/day, with minimal precipitation. Evapotranspiration averaged 0.625 cm/day (FAO Penman-Monteith), leaving 0.094 cm/day for infiltration and storage. Soil-moisture decreased in response to atmospheric demand, particularly in shallow soils. Water-storage capacity across all soil types was driven by groundwater depth, which ranged from 15-76 cm (SSURGO database) to 5 m (CWS monitoring well). Estimated groundwater depths translated into limited storage capacity (2-14 cm) using SSURGO values, with greater storage capacity (25-30 cm) based on measured groundwater depths. Since irrigation occurs during the summer, when groundwater levels are lowest and soil-water storage capacity is highest, the estimated time required to replenish soil-water is likely to exceed a single irrigation season. This suggests that the irrigation rates as applied are unlikely to influence groundwater.
These findings underscore the importance of soil and groundwater interactions in managing recycled water, offering insights for evaluating groundwater recharge potential, optimizing irrigation, and identifying suitable sites for water reuse in future wetland restoration projects.