Sedimentation and internal phosphorus loads in Krishnagiri Reservoir, India

Abstract

This study examines sedimentation rate and its consequences on the bathymetry, capacity and internal phosphorus loading of Krishnagiri Reservoir in Tamil Nadu, South India, utilizing an acoustic Doppler profiler and remote sensing data in an ArcGIS environment. There was a significant change in the reservoir bathymetry for the year 2012, compared with the 2007. The sedimentation rate was 0.818 MCM from 1960 to 1990 and 0.83 MCM over past 5 years. The present reservoir volume is 35.57 MCM, having been reduced to nearly half of its original capacity over a 55 year span, pointing to a seriously threatened lifespan. The sediment total phosphorus (TP) load spatially varied from 6.84 to 23 394 kg, depending on the sediment deposition zones. Sequential extraction indicated the dominance of phosphate fractions to be Al‐P> Fe‐P> Ca‐P> SRP, with an average TP value of 27.27 mg g−1 dry weight. Aluminium‐ (35%) and iron(25%)‐bound forms are the major sediment phosphorus fractions, suggesting temperature, pH and redox or related chemical reactions may be important means of sediment P release in Krishnagiri Reservoir. The sediment phosphorus load in Krishnagiri Reservoir is estimated to be 44.50 tons, with an average TP release of 40.97 mg m−2 (range of 10.22–70 mg m−2). The measured pore water TP concentration and calculated sediment phosphate release exhibited a linear relation. Even with a reduced external P load, the eutrophication of Krishnagiri Reservoir cannot be reduced immediately because of its high internal load and nutrient remobilization.

Mapping the chlorophyll‐a concentrations in hypereutrophic Krishnagiri Reservoir (India) using Landsat 8 Operational Land Imager

“…The higher total phosphorus concentrations measured during the NEM and SWM seasons indicated an increased total phosphorus input from the catchment inflows. Krishnagiri Reservoir's internal phosphorus loading rate is relatively high and directly proportional to its anoxic area (Arunbabu et al, 2014). The total phosphorus concentrations were higher near the structure and middle of the reservoir surface area (i.e.…”

“…The Ponnaiyar River drains this medium‐sized storage structure that serves multiple purposes ranging from irrigation to fish culture. Previous studies by Arunbabu et al (2014) indicated the internal phosphorus loading rate was relatively high, being directly proportional to its anoxic area that led to eutrophication of the reservoir. This eutrophication is supported by the fact that the tilapia o massambius species of fish, which strives in water containing high nutrient concentrations are present in great numbers in this reservoir.…”

“…The Chl-a concentration was found to be higher during August 2017 and September 2017, with a higher concentration during September 2017, compared to the former. There were incidences of fish kills in September attributed to increased cyanobacterial blooms resulting from decreased dissolved oxygen concentrations (Arunbabu et al, 2014) that made the water hazardous for fish survival. The total inflow volume from the catchment was 37.9 MCM during August 2017, whereas the inflow volume was significantly increased to 132.0 MCM because of high rainfall in the catchment area ( Table 3) Carlson (1977) index, which is consistent with the results of previous studies (Ambujam & Sudha, 2016) carried out in the reservoir.…”

Spatial and temporal sedimentation changes in the Three Gorges Reservoir of China

“…; Arunbabu et al . ). Analysis of measured sediment data in and out of the TGR indicated that sedimentation within the TGR is far less than that projected by numerical models utilized prior to when the dam was built.…”

“…Sediment transport obviously controls a reservoir's lifespan (Tarela & Men endez 1999;Morris et al 2006;Zeleke et al 2013;Arunbabu et al 2014). Analysis of measured sediment data in and out of the TGR indicated that sedimentation within the TGR is far less than that projected by numerical models utilized prior to when the dam was built.…”