SIMULATION OF GROUNDWATER DYNAMICS USING VISUAL MODFLOW IN NAGARJUNA SAGAR RIGHT CANAL COMMAND
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Date
2021-09-07
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Abstract
Water is one of the most important and essential natural resources for sustaining human life through agricultural, economical and industrial growth. Rapid growth in industrialization, urbanization and rise in population resulted in decrease of per capita water availability. Nowadays climate change and variability in distribution and occurrence of water affect the sustainable development of the water resources. Sustainable groundwater development and management is a challenge under the present population growth, climate change and land degradation conditions. Groundwater models are playing an important role in decision making to achieve goals through assessment of groundwater potential and future scenarios Hence, a study has been carried out for assessment of groundwater potential in Nagarjuna Sagar Right Canal (NSRC) command area using regional groundwater balance method. The required data was obtained from various government departments such as groundwater, water resources and the Directorate of Economics and Statistics. The gross and net groundwater recharges have been calculated using the regional groundwater balance equation. The negative net groundwater recharge was observed in the study area and estimated as - 2768.32 ha-m per annum which resulting in the declining trend of the groundwater table over the study period in the study area. Groundwater model visual MODFLOW was used to simulate the groundwater levels in NSRC command. Visual MODFLOW was used to simulate the groundwater levels in NSRC command area. The Visual MODFLOW was calibrated and validated using observed groundwater levels for the periods 2008-09 to 2012-13 and 2013-14 to 2016-17 respectively. During calibration, sensitivity analysis has been performed. The recharge is the most sensitive parameter among the other parameters for simulation of groundwater dynamics for the study area. The storage properties and hydraulic conductivity were identified as moderately and less sensitive parameters respectively.
The validated groundwater model was used to predict the groundwater levels in the study area for the years 2020, 2030 and 2040 with different recharge scenarios. Global climate model was used to generate future weather data. MarkSim developed by the International Centre for Tropical Agriculture (CIAT) was used to generate the weather parameters like maximum and minimum temperatures for the years 2020, 2030
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and 2040. The different recharge scenarios with average, lowest and highest recharge over the study period and projected evapotranspiration have been used and revealed that the groundwater levels increase with the increase in recharge and decreases with the decrease in recharge. The storage of available static groundwater resources with an average recharge in the study area would be expected as 2184744.28 ha-m, 2169542.29 ha-m and 2148911.00 ha-m for the years 2020, 2030 and 2040 respectively. Delineation of waterlogged areas and depleted areas in study area was carried out using the contour maps of the depth to water levels and contour maps of groundwater fluctuations. The waterlogged area decreased during pre and post-monsoon seasons over the study period i.e. from 2008-09 to 2016-17. There is no water logging problem identified in the study area with projected weather data in future. The groundwater depleted area was increased in future with all recharge scenarios. Further, Visual MODFLOW used to simulate the impact of change in land use land cover on groundwater resources. The model was used to simulate the groundwater dynamics with future possible scenarios. The storage of available static groundwater resources with the scenario 50 per cent rice converted into ID crops would be expected as 2441006.54 ha-m, 2472496.39 ha-m and 2464895.39 ha-m for the years 2020, 2030 and 2040 respectively. Similarly, the storage of available static groundwater resources scenario with 100 per cent rice convert into ID crops would be expected as 2183658.43 ha-m, 2166284.72 ha-m and 2149996.86 ha-m for the years 2020, 2030 and 2040 respectively. Four scenarios were proposed with the combination of recharge and groundwater pumping. The declined groundwater table was observed with all scenarios and depleted groundwater resources. The storage of available static groundwater resources with scenario -1would be expected as 2118507.01 ha-m, 2108734.29 ha-m and 2100047.44 ha-m for the years 2020, 2030 and 2040 respectively. For scenario - 2, the storage of available static groundwater resources would be expected as 2079416.16 ha-m, 2051183.87 ha-m and 2024037.45 ha-m for the years 2020, 2030 and 2040 respectively. For scenario – 3, the storage of available static groundwater resources would be expected as 2051183.87 ha-m, 2029466.73 ha-m and 1974088.03 ha-m for the years 2020, 2030 and 2040 respectively, For scenario – 4, the storage of available static groundwater resources would be expected as 2004492.02 ha-m, 1974088.03 ha-m and 1951285.03 ha-m for the years 2020, 2030 and 2040 respectively. The impact of change in land use land cover and climate change on the groundwater resources can be mitigated by implementing the preventive measures in the study area. The groundwater depleted area was increased in future with all future possible scenarios. The deeper groundwater table would be expected in future at Chimakurthy and Thalluru villages of Prakasam district and Karempudi and Piduguralla villages of Guntur district in the study area. For improving the groundwater resources, there is a need to establish rainwater harvesting structures in those villages and suggested to construct these structures immediately to avoid the problem of depletion of groundwater resources. The depletion of groundwater in the whole study area can be prevented by the implementation of preventive measures like change in cropping pattern, proper irrigation water management, plantation, construction of artificial recharge structures and water conservation structures.
Description
SIMULATION OF GROUNDWATER DYNAMICS USING VISUAL MODFLOW IN NAGARJUNA SAGAR RIGHT CANAL COMMAND