Estimation of Crop Water Requirements, Demands and Supplies in Chintakani Major Distributary Command of Nagarjuna Sagar Project
Abstract
Considering the promising demand for water in agricultural practices and other applications, efficient use of water has emerged as a critical necessity. This study focuses on the estimation of weekly irrigation water requirements for major crops in the Chintakani major distributary of Nagarjuna Sagar project (NSP) over the period of 2015 to 2018. The methodology employed in this study involved the calculation of reference evapotranspiration using FAO Penmen-Monteith, which is a standard method for estimating evapotranspiration. The results revealed that the average irrigation requirements for Maize and Chillies during the rabi season were 483.12 mm and 898.95 mm respectively. To understand the water dynamics in this region, data pertaining to the weekly canal water during the years 2015-16 to 2017-18 was collected. This data was then used with the estimated demands of crops in the distributary command to assess the adequacy of water supply in meeting the irrigation needs. The analysis of this research revealed that the annual demands of crops during the years 2015-16 to 2017-18 were 1086880, 7956889, 8048374 mᶾ respectively. In contrast, the canal water supplies during the same period were 949440, 7891552.46, 6986024.89 mᶾ respectively. A key finding of this study was the identification of a severe water deficit during the years 2015-16 and 2017-18. This deficit was attributed to a lower amount of rainfall during these years, based on the agricultural practices and climatic variations of the region. This study underscores the urgent need for strategies aimed at enhancing the efficiency of water use in agriculture, particularly in regions prone to rainfall deficits.
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Introduction
Rainfall in India varies in terms of time and location, leading to floods in some areas due to excessive rain, while some regions face severe drought. The rising demand for water resources in agriculture and other sectors is increasing for its beneficial use of water use efficiency. Traditional irrigation methods like border, furrow, check basin, and flood irrigation, which rely on gravity for water delivery, often result insignificant water losses and don’tensure good water distribution. For optimal crop yield, it is essential to manage groundwater and surface water effectively. The choice of technology is influenced by various factors such as the specific location, soil types, crop species, water availability, cropping pattern, climate, socio-economic conditions, etc. Urban areas and industries often get priority in water allocation, which can intensify the impact of supply shortages on irrigated areas during years of water deficit. The way these temporary and chronic shortages are spread across the command area will determine their overall effect on agricultural production and the livelihoods of farmers within the irrigated command area (Gaur et al., 2008).
Evapotranspiration (ET) plays a crucial role in the water cycle and is vital for interpreting soil surface phenomena in climatology. It is directly related to productivity in ecosystem and agricultural research (Chen et al., 2005). The water requirement of crops varies based on the season, crop stage, management approaches and cultivation area. Calculating these crop needs involves factors like ET and crop coefficients (Gadge et al., 2011). Gaur et al. (2008) conducted an integrated approach to assess how cropping patterns and the spatial equity of canal flow changed with water supply in the left canal command area of Nagarjuna Sagar. They found that water scarcity resulted in 40% land being followed in the left-bank canal command area and suggested that equitable allocations could be achieved by improving the water distribution efficiency of the canal network during normal years and by crop diversification and introduction of alternative water sources during water shortage years.
Venot et al. (2010) examined the strategies of farmers in Nagarjuna Sagar Project during drought periods. They used semi-structures interviews and field observations to collect data from 30 farmers indifferent zones of the command area and found that farmers adopted various practices such as irrigation scheduling, water harvesting, agroforestry, and market linkages to cope with water scarcity and maintain crop productivity. Kumar and Madhnure (2021) explored the potential of conjunctive use of surface and groundwater in left bank canal command area of Nagarjuna Sagar Project, a case study from Khammam district, Telangana state. They found that conjunctive use of surface and groundwater could enhance water availability and reduce conflicts among different users.
Crop water requirements of the major crops grown in Bhimsagar command area as assessed by CROPWAT 8.0 software (Rajput et al., 2018) prepares a rotational water allocation plan for Ratnapura minor located on the right main canal. Rajput et al. (2018) developed a plan that helped in the proper operation of the system for better utilization of water resources and improved crop productivity. Rao and Rajput (2009) proposed a decision support system for can water releases for reducing the gaps between canal supplies and demands for increasing the water use efficiency in canal command areas. Also provided guidelines and suggestions under different situations of water deficit or surplus. Sravya et al. (2019) used the optimization techniques to estimate the crop water requirements, demands and supplies in D-51 distributary command of Sri Ram Sagar project. Conjunctive use planning is a strategy to optimize the use of water resources indifferent sectors, such as agriculture, industry, and environment.
Lingo software was used to develop an optimization model for conjunctive use planning in the Upper Damodar River basin in India, which is a major river basin with high water demand and low water availability (Jha et al., 2020, Sabale et al., 2022). This algorithm optimizes the water allocation among different sectors such as irrigation, domestic use, and environmental flow for achieving conjunctive use of ground and surface water resources. The concepts, principles, benefits, challenges and strategies of conjunctive use of surface and groundwater resources were proposed (Sabale et al., 2023). Afshar et al. (2021) assesses the adaptability of cyclic and non-cyclic approach to conjunctive use of ground and surface water for sustainable management plans under different climate change scenarios. The present study was conducted using the analysis of surface and groundwater resources in the Chintakani canal command area of Nagarjuna Sagar project.
Conclusion
The weekly irrigation water requirements of the major crops were estimated in the selected Chintakani major distributary of NSP during the years 2015 to 2018 using FAO Penmen – Monteith method. The average gross irrigation requirements of Maize and Chillies of Rabi season were found 483.12 and 898.95 mm. The yearly demands of crops during 2015-16 to 2017-18 are 1086880, 7956889, 8048374 mᶾ and canal water supplies are 949440, 7891552.46, 6986024.89 mᶾ. There was a severe deficit of water during the years 2015-16 and 2017-18 due to less amount of rainfall.
