ASSESSMENT OF SURFACE WATER RESOURCE IN SAMASTIPUR DISTRICT OF BIHAR USING RS AND GIS
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Date
2021
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DRPCAU, PUSA
Abstract
The study region, Samastipur district of Bihar surrounded by 5 km buffer zone was divided into 67 square grids of 8 km × 8 km spatial resolution using (ArcGIS) software version 10.7.1. The monthly rainfall images (TRMM_3B43) for the period of 20 years from the years of 2000 to 2019 and the monthly dataset of LST (GLDAS_NOAH025_M_EP) products of 0.25o × 0.25o grid size for the period of 21 years from 2000 to 2020 were downloaded and used for analysis. The climatic variables viz. monthly rainfall and LST values were extracted for all grid points (GP-1 to GP-67) using the model builder tool of ArcGIS. Following the recommendation of WMO, the 14 grid points between GP-44 and GP-66 falling under the circumferential coverage of 3000 km2 (radius of 30.90 km) in flat area from MS, Pusa were considered for comparison and validated with ground-based climatic variables measured at MS, Pusa. The graphical technique and statistical techniques like Pearson correlation coefficient (PCC), mean error (ME), root mean square error (RMSE), bias (B), and Percent bias (PB) were used for comparison. Bias in extracted climatic variables was identified and was corrected using linear scaling.
The Landsat-8 imageries were used to develop LULC using supervised classification technique in ArcGIS. The accuracy assessment was carried out using visual observation, Google Earth image, mathematical analysis and the kappa coefficient. The validated soil map of the study area was procured from NBSS and LUP, Nagpur, India and reclassified into soil textural classes. The available water capacity (AWC) of the soil was computed based upon the land use, soil texture and rooting depth following the suggestion of Thornthwaite and Mather (1957). The surplus and deficit water for all the grid points area was estimated using computed monthly PET, AET and AS as input parameters. Thematic maps of potential evapotranspiration, actual evapotranspiration and availability of surplus and deficit water over the study area were developed using inverse distance weighted interpolation technique of ArcGIS.
The study investigated that estimated PET was progressively increasing from January to June and thereafter gradually decreasing from July to December. PET was found maximum (120.7 mm) for the month June and minimum (5.5 mm) for the month January and similar pattern were observed in case of AET. During the months of July (85.3 mm), August (83.9 mm) and September (81.1 mm), AET and PET were found to be equal. The LULC map depicted the five types of land use feature classes viz. agricultural land, barren land, forest land, settlement and water body in the region. Silt loam, clay loam and clay were observed as major soil textural classes distributed in the study region. The study area undergoes an annual water deficit of 121.2 mm distributed during the months of February to May, November and December whereas, the annual water surplus of 523.8 mm during the months of January, July to September.