Assessment of impact of aquaculture on Kolleru Lake (India) using remote sensing and Geographical Information System

Aquaculture is one of the fastest growing food industries 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 aquaculture. To assess the impact of aquaculture on Kolleru, satellite data were found appropriate because of the synoptic-detailed overview and accuracy. Satellite 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 verified in the field 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 km(2), in which 70.70 km(2) had water throughout the year and 100.97 km(2) had water during the rainy season. The digital image processing of 2004 satellite data revealed that Kolleru was no longer a lake and the lake area of 62.65 km(2) (34.73%) only remained in a degraded state, extensively colonized by macrophytes. The total loss of lake area was 109.02 km(2) between 1967 and 2004, in which aquaculture was developed in 99.74 km(2), 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 km(2) in 2004, the increase in lake area for agriculture between 1967 and 2004 being 8.22 km(2) (4.55% of lake). If human induced degradation is allowed to continue, 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-development 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.