Establishing Water Surface Area-Storage Capacity Relationship of Small Tanks Using SRTM and GPS

Abstract

In Semi arid regions of India, small storage structures such as village ponds and tanks capture the surface runoff during the monsoon season to exploit in dry season. Rarely this could be considered in the water resources system planning, even though they are important sources of water supply for multiple uses. With the increase in human population, these storage structures are encroached upon by the local residents resulting in loss of capacity. The main limitation in considering the effects of these structures are the lack of knowledge on existing small storage structure distributions and their storage capacities. The methodologies now being used to quantify physical parameters of small tanks are costly, time consuming, as well as laborious. To address this challenge an attempt is made to estimate the small storage tank capacities as a function of their surface areas using Shuttle Radar Topographical Mapper (SRTM) data set of global elevations of 90m Digital Elevation Model (DEM). However, overall assessment of the accuracy of this product involving ground truth control and accuracy verification methods with higher level of precision, like as the Global Positioning System (GPS). A field study of 14 small tanks was carried out using a GPS and an engineering survey in the Sindapalli Uppodai Subbasin of the Vaippar River basin, Tamil Nadu, India. A regression analysis was carried out to establish a power relationship between surface area and storage capacity of small tanks. The root mean square error (RMSE) of the analysis obtained from the equation is within the acceptable limit of 10%–15% and also the correlation obtained between the field survey and SRTM volumes is acceptable even though the resolution is less (90m x 90m grid size).