NL-CAT - Nutrient Losses at catchment scale

In the Netherlands the model STONE (Wolf et al., 2003) is used to assess the (long term) impact of nutrient management strategies and manure legislation on nitrate concentrations in groundwater and nutrient load of surface water systems on national scale (Schoumans et al., 2004). This STONE model consist of a fertilizer and manure distribution module (CLEAN or MAMBO), an hydrological model (SWAP) and a soil-water quality model (ANIMO). With this model the nutrient losses from agricultural land and nature areas to surface water can be quantified. However processes and transport in surface waters are not modeled with the current STONE -model chain for national evaluations. In order to evaluate the impact of different type of measures on the improvement of the surface water quality and validation studies on surface water quality parameters at catchment scale, also the surface water modeling have to be taken into account. For this reason the model chain NL-CAT (Nutrient Losses at catchment scale) was built (Schoumans et al., 2005) that consist of the two important STONE components SWAP and ANIMO in combination with a surface water quantity and a surface water quality module. The SWAP module (Kroes and Van Dam, 2004) is used to generate hydrological input to the ANIMO module (Groenendijk et al., 2005) ANIMO simulates the nutrient cycle in soil and the nutrient leaching to groundwater and surface waters. Surface water discharges are simulated by the SURFACE WATER module (Smit et al., 2005). Finally, simulation of surface water quality processes and retention within a (large) catchment is performed by the NUSWALITE module (Siderius et al., 2005). To quantify the amounts of P (and optionally N) added to the surface water system via surface erosion, the NL-CAT model has been extended with a simple erosion module; P-USLE. This module is based on the modified and revised Universal Soil Loss Equations and implemented in a GIS-environment (Walvoort, 2004).