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Abstract
Abstract. Hydrologic climate change modelling is hampered by climate-dependent model parameterizations. To reduce this dependency, we extended the regional hydrologic modelling framework SIMGRO to host a two-way coupling between the soil moisture model MetaSWAP and the crop growth simulation model WOFOST, accounting for ecohydrologic feedbacks in terms of radiation fraction that reaches the soil, crop coefficient, interception fraction of rainfall, interception storage capacity, and root zone depth. Except for the last, these feedbacks are dependent on the leaf area index (LAI). The influence of regional groundwater on crop growth is included via a coupling to MODFLOW. Two versions of the MetaSWAP-WOFOST coupling were set up: one with exogenous vegetation parameters, the "static" model, and one with endogenous crop growth simulation, the "dynamic" model. Parameterization of the static and dynamic models ensured that for the current climate the simulated long-term averages of actual evapotranspiration are the same for both models. Simulations were made for two climate scenarios and two crops: grass and potato. In the dynamic model, higher temperatures in a warm year under the current climate resulted in accelerated crop development, and in the case of potato a shorter growing season, thus partly avoiding the late summer heat. The static model has a higher potential transpiration; depending on the available soil moisture, this translates to a higher actual transpiration. This difference between static and dynamic models is enlarged by climate change in combination with higher CO2 concentrations. Including the dynamic crop simulation gives for potato (and other annual arable land crops) systematically higher effects on the predicted recharge change due to climate change. Crop yields from soils with poor water retention capacities strongly depend on capillary rise if moisture supply from other sources is limited. Thus, including a crop simulation model in an integrated hydrologic simulation provides a valuable addition for hydrologic modelling as well as for crop modelling.
Highlights
In hydrologic models, vegetation characteristics are usually defined by “exogenous” parameters; a fixed dependency on the days of a year is assumed
The resulting limitations on the model validity become more poignant with the advent of climate change impact modelling using scenarios
These scenarios usually differ widely from current climate, which increases the necessity for endogenously simulating the weather- and climate-dependent vegetation feedback to the hydrologic system
Summary
Vegetation characteristics are usually defined by “exogenous” parameters; a fixed dependency on the days of a year is assumed. The resulting limitations on the model validity become more poignant with the advent of climate change impact modelling using scenarios These scenarios usually differ widely from current climate, which increases the necessity for endogenously simulating the weather- and climate-dependent vegetation feedback to the hydrologic system. The soil water submodel is a very simple two-layer type which cannot simulate capillary rise This severely limits its applicability for simulations that require a feedback loop via groundwater. Another example of a regional integrated model is PROMET (Mauser and Bach, 2009). This approach to soil water modelling lacks sophistication.
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