Water hyacinth growing in the lakes absorbs the nutrients (phosphorous, nitrogen) being released to the lake water from untreated sewage discharged in the lake, for their growth and reduces the nutrient concentration in the lake water. After a period of time these plants sink to the bottom of lakebed and decay affecting water quality.

The effect of sand mining on the economic performance of groundwater irrigation has been studied in the Panruti taluk of Cuddalore district in Tamil Nadu. A comparison of water productivity for different farms-size categories has been done in sand mining and non-sand mining blocks. The cropping sequence, cropping intensity, irrigation particulars, investment pattern on tubewells, use of different HP-motors, etc. have been studied in sand mining and non-sand mining blocks.