A Pioneering Assessment on the Physico-chemical and Health Status of a Small Sub-tropical Reservoir in North-Eastern, India

Background: The water resources of Northeast (NE) Indian reservoirs have been largely overlooked, despite their immense potential in various aspects. A comprehensive analysis of water quality parameters was conducted to assess the physio-chemical changes and health status of Maphou or Mapithel reservoir, Manipur, NE, India. Methods: Sub-surface water samples were collected from June 2021 to May 2022 to assess the spatio-temporal changes. Trophic State Index (TSI), Morpho Edaphic Index (MEI), Maximum Sustainable Yield (MSY) and fish yield potential were calculated. The average water spread area was calculated through Normalised Difference Water Index (NDWI) method. Result: A total of eighteen (18) water quality parameters were examined following Standard Methods. ANOVA analysis indicated that all water quality parameters, except total alkalinity, exhibited significant seasonal variations (p less than 0.05). Spatially, most of the water quality was found to be insignificant, except for Chl-a and depth (p less than 0.05). All the water quality parameters were within acceptable ranges for the growth and survival of aquatic biotic resources. No signs of pollution were observed. The trophic status of the reservoir was found in an oligotrophic state. The MEI was estimated as 8.55 and the average fish yield for the reservoir was 14.98 kg ha-1, which is below the national average yield of small reservoir (49.9 kg ha-1). The MSY was estimated to be 21.46 kg ha-1. Heatmap cluster analysis revealed three distinct clusters of months. The actual average water spread area was determined to be 852.62 ha, hence the reservoir can be categorised as small reservoir.