Assessment of Reduction in Water Spread of Shanthisagara Lake in Davanagere District Karnataka using Geoinformatics

The aim of present study is to assess the causes for reduction in water spread of Shanthisagara lake in Davanagere district from the last 50 years using Remote Sensing and GIS techniques. The remote sensing data like, Landsat-5MSS, Landsat-7ETM+ and Resourcesat-2, LISS-IV were used to map the water spread area of the lake. Multidate satellite data analysis showed that, there is change in lake water spread over the years. To know the reasons, rainfall data for more than 50 years were collected and analyzed along with Land use/ Land cover studies carried out using LISS-IV data for the year 2009 and 2018. The result infers that, there is a reduction in water spread area of Shanthisagara lake over the years is due to reduction in rainfall in the catchment area and significant change in Land use/Land cover pattern from year 2009 to 2018 has also contributed to reduced inflow to lake.


INTRODUCTION
Lake is an area filled with water localized in a basin, which is surrounded by land, apart from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, and therefore are distinct from lagoons, and are also larger and deeper than ponds, though there are no official or scientific definitions. Lakes can be contrasted with rivers or streams, which are usually flowing. Most lakes are fed and drained by rivers and streams. (Kalaiselvanet.,al 2018) Natural lakes are generally found in mountainous areas, rift zones, and areas with ongoing glaciation. Other lakes are found in endorheic asins or along the courses of mature rivers. In some parts of the world, there are many lakes because of chaotic drainage patterns left over from the last Ice Age. All lakes are temporary over geologic time scales, as they will slowly fill in with sediments or spill out of the basin containing them. Many lakes are artificial and are constructed for industrial or agricultural use for hydroelectricity power generation or domestic water supply or for aesthetic, recreational purposes or other activities.

IMPORTANCE OF THE STUDY
The study reveals the causes for the reduction of water spread area in the lake over the years using satellite remote sensing data (from last 50 years) either rainfall over 50 years or the impact of LU/LC patterns changes in the lake catchment area.

Data Used:
The change in the water spread area has been studied using multi-temporal satellite datasets used is as given in Table 1. Institute) creates and analyzes geographic data, tests predictions and ultimately makes better decision which allows a user to visualize and manage the database. ArcGIS is used by people all over the world to put geographic knowledge to work in government, business, science, education and media. ArcGIS enables geographic information to be published so it can be accessed and used by anyone.
ERDAS Imagine: High resolution images are used to analyze the Land use/Land cover changes using ERDAS, because of the popularity and wide acceptance in remote sensing image classification. In this project, ERDAS imagine is used for the purpose of geo-referencing.

LU/LC Pattern of Shanthisagara Lake Catchment Area of Year 2009
Land use Land cover map (Fig 9)

LU/LC Pattern of Shanthisagara Lake Catchment Area of Year 2018
Land use Land cover map (Fig 10)    CONCLUSION Remote sensing and GIS techniques are very useful to assess the change in water spread and LU/LC of given area. Multi-dated Satellite data for the last 50 years has enabled mapping of watershed of Shanthisagara Lake. Rainfall analysis for the last 50 years showed that, rainfall has reduced over the 50 years and it could be one of the reasons for the reduction in water spread area of the lake. Land use/Land cover change analysis has shown that there is significant increase in plantation area and this is may be one of the reasons for reduced inflow to the lake. The suggestion like desiltation of the streams, those connecting to the lake will enable to good flow of water to the lake which may leads to increase the water spread area.