Understanding the Impact of Climate Variability on Agricultural Water Requirement

Climate change and its variability will affect the agricultural water availability as well as overall crop yield due to change in evapotranspiration and irrigation water demands by crops. Long term climate variability may lead to the shift in planting and harvesting dates (crop duration) and ultimately changes the overall cropping pattern. The current research deals in simulating the effect of short and long term climate variability on agricultural water requirement and crop yield using a field and catchment scale hydrological model for Germany. This was performed by comparing the amount of agricultural water requirement and crop yield simulated by two hydrological models (SWAT: Soil and Water Assessment Tool and SWAP: Soil, Water, Atmosphere and Plant) against the expert based irrigation amounts from 2006-2018. Landwirtschaftskammer is the agricultural chamber of the Federal State of Lower Saxony which operates different experimental fields in Hamerstorf within the Ilmenau River catchment (Germany). The mentioned duration comprises of extremes (e.g., 2017: no or minimal irrigation applied; 2018: extreme drought condition) as well as average climatic conditions. SWAT was calibrated at catchment's outlet using daily observed streamflow data from 1980-2000 along with the soil moisture (gravimetric) of one plot for the years 2009-2010 (first 30 cm soil profile) whereas SWAP was only calibrated using soil moisture data. The modeling results revealed that the observed crop yield from the experimental fields was underestimated for most crops for both the models by using standard parameters. The energy based crop growth model fails in both the models. Therefore, in order to predict the agricultural water requirement and crop yield under future climate change, time variable growth stage parameters need to be incorporated into the model. The final results will propose a change in the plant parameters based on the past studies for future climate. In addition, how the developed models have performed during the extreme events. The proposed objective will be beneficial for the agricultural community to use agro-hydrological models to predict, control and advise the amount of irrigation water requirement under future climate change.