Implementation of a coupled agricultural landscape model to predict water, carbon and nitrogen fluxes on the catchment scale

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Water plays a dominant role in the distribution and re-distribution of energy, nutrients, pollutants and soils across all landscapes. It directly regulates plant growth, creates floods and drives trace gas emissions from soils. In agriculture, farmers base their management decisions on soil moisture to reduce soil compaction or on precipitation to avoid pesticide losses - water is an indirect driver of these decisions. Hydrological states and processes that regulate the direct and indirect drivers are highly variable in space and time. If we want to better understand the intrinsic interaction of water and associated matter fluxes in landscapes, or if we want to test hypotheses such as “what happens...if”, models are perfect tools to help us studying processes and solve these questions. While many models have been developed for particular ecosystems, we are lacking comprehensive tools to study the many possible feedback mechanisms and lateral interaction of ecosystem components across landscapes. Here we aim at setting up such a modeling tool. The proposed hydrological Catchment Model Framework (CMF) is based on an open source, modular modeling structure, following a fully distributed and deterministic approach. CMF allows coupling specifically developed models but also the buy-in of already available ones. In particular, we will implement models that simulate hydrology, biogeochemistry, pesticide transport and fate, agricultural management as well as plant and tree growth. Several of these models have already been built, e.g. within a preliminary DFG research project (BR 2238/7-1) and the EU Integrated Project NitroEurope. These models provide the core of this proposal. A pesticide fate model is not at hand yet and will be developed based on the applicant´s experience with PRZM and MACRO. A full coupling of the different models and testing of the resulting multi-model with real world data is the final goal of this project. We will apply CMF in the Schwingbach, a 25 km² sized catchment of central Europe. The catchment is intensively used for agriculture downstream while the headwaters are covered by forests and grasslands. Many hydrological and biogeochemical measures have been monitored since 2010 when the experimental study area “Studienlandschaft Schwingbachtal” has been established. Pesticide concentrations will be measured to obtain a sound data set for pesticide fate model validation. To proof whether the spatial and temporal dynamics of processes are captured by CMF, we will study hot spots and hot moments of pesticide concentrations and N stream concentrations. We will end our research program with the evaluation of management scenarios and investigate their impact on catchment scale water, nutrient and pesticide fluxes.