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Drained peatlands have peculiar hydrological properties and cause environmental concerns due to carbon dioxide emissions and nutrient fluxes resulting from decomposition of organic matter in peat. As peat degradation is strongly controlled by soil moisture conditions, it is assumed that flexible water management methods, such as controlled drainage, can be used to reduce the environmental impacts of drained peatlands in agriculture. While peat soils have been extensively researched, there is a need for increased understanding about the hydrological responses of peatlands to various water management schemes. Research is needed to quantify these responses, and a promising approach is to exploit simulation models for describing peatland hydrology at field scale. The goal was to calibrate and validate a hydrological model FLUSH to describe the hydrology of an agricultural field block having a shallow peat cover and managed with controlled drainage. FLUSH is a spatially distributed three-dimensional (3D) process model which simulates the hydrology of agricultural fields managed with controlled subsurface drains and open ditches. The soil description of FLUSH includes both soil matrix and macropores accounting preferential flow. Richards equation and Mualem-van Genuchten water retention model are applied for subsurface flow. The modeled field block is located in Ruukki, northwestern Finland, and the study period was from August 2018 to October 2021. Groundwater table depth and drain discharge observations were used for the calibration and validation. The Kling-Gupta efficiencies for the simulated groundwater table depths in soil matrix and macropore domains were 0.50 and 0.47, respectively, during the calibration period, and 0.23 and 0.33 during the validation period. The efficiency values for the simulated drain discharge during the calibration and validation periods were 0.18 and 0.19, respectively. Limiting the modeled area to the block lead to cumulative drain discharges clearly smaller than the observations. The underprediction was improved by extending the modeled area beyond the block, which suggested a presence of a hydrological connection in terms of groundwater flux originating from outside the block. Thus, the surrounding environment can play a role in the hydrology of peatland fields, and this should be considered in water management design. Despite the large difference between observed and simulated cumulative drain discharges, the main hydrological dynamics were captured, and the model formed a useful tool to simulate drainage scenarios in peatlands and to study the role of the surrounding areas on field hydrology.

Soil erosion reduces the sustainability of agricultural sector by loss of productive soil and through negative impacts on surface waters. In Finland, considerable efforts have been made to reduce soil erosion, but the suspended sediment loads to surface waters have not markedly reduced. A major limitation has been the lack of high-resolution data on erosion risk for efficient targeting of the erosion management efforts. In this study, by using the Revised Universal Soil Loss Equation (RUSLE) a two-meter resolution erosion risk data was developed and consequently the spatial distribution of the erosion risk of Finnish agricultural land was analysed. With agricultural management practices of 2019, the average erosion of agricultural land was estimated to be 430 kg ha−1 yr−1, and it varied at the municipality scale from 100 to 1290 kg ha−1 yr−1. At more local scales the erosion risk had even greater variability, and areas with high erosion risk were differently located in terms distances to water bodies. The results also suggest that the past erosion management efforts have not been well-targeted according to the actual erosion risk. Altogether, the results indicate that erosion mitigation measures can be improved by inclusion of high-resolution data in the planning and implementation of the measures, by considering the spatial variability of the erosion risk over multiple spatial scales, and by implementation of location specific erosion reduction measures.