Indicators of sustained agriculture, impacts of LULC and weather parameters on ET: Case study in Chota Nagpur Plateau

Abstract

Land use land cover (LULC) modification due to anthropogenic and climate change affects evapotranspiration (ET) and consequent crop yield. Ranchi region in the Chota-Nagpur Plateau is vulnerable to deforestation and land degradation caused by urbanization, though agriculture is a sustainable livelihood. The study deals with the long-term assessment of LULC changes and other relevant parameters and their impact on ET during the major cropping season in the station where ET influences crop yield. Landsat 8 OLI high-resolution images during the cropping season (November–March) are processed to determine LULC classes of 'Agricultural area', 'Fallow/wasteland', 'Built-up area' and 'Water body' and their modification in terms of fractional percentage areas over the period 2007–2020. The agricultural area has reduced from 196 sq. km in 2007 to 136 sq.km in 2020, whereas built-up and fallow/wastelands have increased from 13 to 25 sq. km and 95 to 116 sq. km, respectively, during the same period. The impact of LULC change over the years on ET (MODIS16A2) over agriculture crops is assessed by subjecting the yearly time series of ET and other potential influencing parameters like NDVI (MODIS), relative humidity (RH), soil moisture (SM) (NASA Power) and extent of Agriculture area to regression analysis, 'R-squared decomposition'. It is found that the agriculture area contributes about 10 % to the ET variance, whereas NDVI explains 72 %, while SM and RH account for 7 % and 9 % respectively. The study also shows that the area under agriculture has changed minimally. Hence, it becomes crucial to have an ET-based irrigation method to sustain agriculture, which is yet a primary livelihood in the region despite the pressures of urbanization, which is mineral-rich.