Monitoring changing trends of water presence state in the major manmade reservoirs of Mayurakshi river basin, eastern India

Spatio-seasonal water presence frequency and water depth change is tried to identify in two manmade reservoirs (Massanjore dam and Tilpara barrage) over Mayurakshi river of Eastern India. These reservoirs use to supply water for hydroelectricity and irrigation services. Multi-temporal image base analysis in three phases (phase 1:1987–1999; phase 2: 2000–2006 and phase 3: 2007–2016) clearly depicted that (1) in case of Massanjore dam (67.4 km2) water presence area in pre-monsoon season is declined from 44.13 to 23.54 km2 in between phase 1 and 3. (2) In post monsoon season, same is declined from 63.37 to 37.57 km2. (3) In case of Tilpara reservoir, water presence area is declined from 3.61 to 2.20 km2 in pre monsoon season and 3.76–2.67 km2 during post monsoon season since phase 1–3. Both average and maximum NDWI scores indicating qualitative depth of water in pre and post monsoon seasons have declined over time with significant rate (R2 ranges from 0.42 to 0.58). All these indicate growing attenuation of water availability within reservoirs. This may invite hardship to the stakeholders depends on the reservoir and ecological set up of the reservoir.