Evaluation of actual evapotranspiration, water surplus and water deficit for climate smart rainfed crop planning in Bihar

Abstract

Agroclimatic study was carried out for the state of Bihar to evaluate actual evapo-transpiration (AET), water surplus (WS) and water deficit (WD) during different seasons viz. kharif, rabi and summer. Thematic maps comprising AET, WS and WD were generated to assess seasonal water use, water surplus and water deficit (high, moderate and low) zones in different districts of Bihar for developing climate smart crop production strategies for rainfed ecosystem. The AET, WD and WS were estimated through climatic water balance method based on historical rainfall data (30-55 years) of 110 rain-gauge stations, normal weekly potential evapotranspiration (PET) and available water holding capacity (AWC) of coarse-, medium- and fine-textured soils. The results revealed that maximum annual AET >800 mm was recorded in Kishanganj, major parts of Araria, Madhepura and Bhagalpur districts and in a small pocket in West Champaran district. The lowest annual AET (<600 mm) was recorded in some pockets of Nalanda district due to low AWC and rainfall. Major parts of Bihar exhibited the annual AET ranging from 600 to 800 mm during kharif season. While considering WS, the districts under Zone II (North-east alluvial plains) recorded the maximum values, whereas the minimum was recorded in Zone IIIB (Part of south Bihar alluvial plains). During kharif season, very low WD (<50 mm) was recorded in West Champaran, East Champaran, Sheohar, Sitamarhi, Madhubai, Supaul, Araria, Kishanganj, Purnia, Madhepura, Katihar, Khagaria, Bhagalpur, Munger, Lakhisarai, Jamui and parts of Banka districts and hence, in terms of better water availability, these districts could be identified as potential rainfed crop growing region in the state. The WD exceeded 100 mm in kharif season in Aurangabad district, parts of Gaya, minor pockets of Jahanabad and Nawada districts. Crop suitability during rabi and summer seasons has also been discussed based on AET, WD and WS. The information emanated from the study could serve as an important guideline in chalking out climate driven tactical and strategic crop planning for augmenting rainfed crop production in the state of Bihar.