Assessment of changes in Kolleru lake in Andhra Pradesh due to the development of aquaculture using satellite data.

Abstract

Aquaculture is one of the fastest growing food indus tries and the rapid growth of aquaculture worldwide has resulted in growing concerns about its impact on important ecosystems. Kolleru Lake, India’s largest fresh water body, and Ramsar site have undergone tremendous changes due to the development of aqua culture. To assess the impact of aquaculture on Kol leru, satellite data were found appropriate because of the synoptic-detailed overview and accuracy. Satel lite data of IRS 1D, LISS III from 2004 and Survey of India topographic maps from 1967 were processed using image processing techniques in ERDAS IMAGINE and analysed in Geographical Information System (GIS) such as ARC GIS 9.1. Land use map prepared from the satellite data was veri¢ed in the ¢eld using Global Positioning System to check the land and water use classes and its areal extent. It was estimated from the topographic maps of 1967 that the total lake boundary area was 180.38 km2 , in which 70.70 km2 had water throughout the year and 100.97 km2 had water during the rainy season. The digital image pro cessing of 2004 satellite data revealed that Kolleru was no longer a lake and the lake area of 62.65 km2 (34.73%) only remained in a degraded state, exten sively colonized by macrophytes. The total loss of lake area was 109.02 km2 between 1967 and 2004, in which aquaculture was developed in 99.74 km2 , which represented 55.3% of the 1967 lake area. The maximum conversion to aquaculture occurred from the lake liable to be inundated during the 1967 rainy season. The area under agriculture was 16.62 km2 in 2004, the increase in lake area for agriculture be tween1967 and 2004 being 8.22 km2 (4.55% of lake). If human induced degradation is allowed to con tinue, the lake will very soon disappear. Now, the Government of Andhra Pradesh, India, has initiated schemes and laws to restore the lake to its pre-devel opment state. Lessons learnt from the Kolleru Lake cautioned that there is a need for regular monitoring of important water resources throughout the world to protect the biodiversity of the earth.