Representing Indian Agricultural Practices and Paddy Cultivation in the
Variable Infiltration Capacity Model
Abstract
Increased irrigation due to agricultural intensification has profound
impacts on the surface water and energy balance at regional to local
scales. Recent updates of the state of the art Land Surface Models
(LSMs) include the impacts of irrigation on surface hydrology. The
Indo-Gangetic Plain (IGP) is one of the global hotspots of irrigation
water applications. However, the direct application of these models to
Indian basins has certain limitations. The commonly employed flood
irrigation technique is often indiscriminate and unmanaged, unlike the
state-of-the-art models’ estimation of crop water use based on soil
moisture conditions. The primary crop in the IGP is paddy, cultivated in
inundated fields with quite distinct water and energy partitioning
mechanisms represented in very few models. Here, we developed an
improved irrigation module to simulate the Indian agricultural practices
for the widely used Variable Infiltration Capacity (VIC) model. We
incorporated the crop-specific water use for flood irrigation,
calculated based on previously reported field studies. The water and
energy balance processes are modified by incorporating the ponded paddy
fields with proper parameterization. We achieved a substantial
improvement in the simulated evapotranspiration and soil moisture of the
IGP, particularly in the non-monsoon seasons with the updated model. We
found that evapotranspiration and soil moisture are more sensitive to
the irrigation techniques than the interval of irrigation application.
Runoff strongly responded to irrigation technique as well as the
interval of application. We emphasize accurate representation of
irrigation practices in the LSMs, specifically when applied to the
human-natural hydrological system.