Quantitative land evaluation implemented in Dutch water management

Both in land evaluation and in water management quantitative methods, GIS and simulation modelling are well-known techniques for quantifying the effects of changes, such as land use or climate change. For hydrological management decisions information is often required on the effect of those decisions on agricultural production. To serve the needs of different types of users, like water authorities, provinces, drinking water companies and the National Department of Infrastructure and Water Management we developed a toolbox named WaterVision Agriculture as an instrument that can determine effects on crop yield and the farm economy as a result of drought, too wet or too saline conditions for both current and future climatic conditions. WaterVision Agriculture is based on the hydrological simulation model SWAP, the crop growth model WOFOST and farm management and economic assessments such as DairyWise for dairy farming. The WaterVision Agriculture (WVA) project resulted in two products, namely i) an easily applicable tool (also called the WVA-table) and ii) the operational models for hydrology and crop growth SWAP and WOFOST for calculating effects on field scale combined with calculating farm economic results and indirect effects. SWAP simulates water transport in the unsaturated zone using meteorological data, boundary conditions (like groundwater level or drainage) and soil parameters. WOFOST simulates crop growth as a function of meteorological conditions and crop parameters. Using the combination of these process-based models and methods for describing crop management and economic value we derived a meta-model, i.e. a set of easily applicable simplified relations for assessing crop growth as a function of soil type and groundwater level. These relations are based on multiple model runs for at least 72 soil units and the possible groundwater regimes in the Netherlands. The easily applicable tool (WVA-table) uses this meta-model. Applying the meta-model of WaterVision Agriculture should allow for better decisions on land use or soil and water management because the instrument can help to quantify the effects of changes in climate, land use, hydrological conditions or combinations of these effects on agricultural production.