CONCLUSION
This study shows that Amruthalli lake was polluted severely by nutrients from streets, sewage and industrial effluents than Rachenahalli lake;and its quantified value and functions are also less than that of Rachenahalli lake. It also shows that people in these areas are very much dependent on these lakes for their daily consumption; and depth and area of both the lakes have been considerably reduced during last two decades, due to siltation and encroachments for developmental activities. Eutrophic condition is seen in Amruthalli lake. Hence there is an immediate need to restore, conserve and preserve these existing wetlands to maintain and improve the ecological balance.
GIS approach provides the decision-makers a powerful tool for collecting, storing, analysing and displaying the information layers of data. Integration of water quality and quantity along with socio-economic and population informations has aided in arriving at appropriate restoration conservation strategies of Rachenahalli and Amruthalli lake waters. Some of the Best Management Practices(BMPs) are suggested in managing and restoring wetlands. It includes the following practices:
- Pollution prevention practices might be applied to reduce the generation of non-point source of pollution and pollution from industrial, residential, agricultural and institutional areas through source reduction, waste minimisation and process control.
- Promoting public education programs regarding proper use and disposal of household and agricultural hazardous waste materials.
- Afforestation around the lake to control the entry of silt from run off.
- Infiltration trenches might be useful in reducing the storm water sediment loads to downstream wetlands by temporarily storing the runoff.
- Extended detention dry basins might be provided in removing pollutants primarily through the settling of suspended solids.
- Constructed wetlands are recommended for the purpose of stormwater management and pollutant removal from the surface water flows.
Apart from this, following restoration methods are also suggested to improve the catchment conditions and the quality of water.
Desiltation, to improve the catchment yield; aerating the lake water and harvesting of macrophytes to improve the quality of water, oxygen content, removal of odor from water and to avoid eutrophication condition;prevention of pollutants like phosphorus, nitrogen, suspended solids, by waste water treatment methods like screening, stabilization pond, aerated lagoon and water harvesting structures with removal efficiency of 50 - 90 % of suspended solids, 25- 75% of total phosphorus and 30-80 % of nitrates; and prevention of encroachments through legal action along with public participation's are suggested. Restored wetlands could be used for recreational purposes such as boating and fishing; and for agricultural purposes, conditioned that care should be taken to maintain the prevention of point and non-point source of pollution that drained in to it.
