Morphmetric Analysis of Randenigala Reservoir catchment using GIS

Abstract

Morphometric techniques play a major role in addressing the quantitative description of the geometry of thedrainage basins and its network. This helps in characterizing the drainage network, comparing thecharacteristics and examining the effect of lithology, rock structure and rainfall. The study focuses onanalysis of morphometric features of Randenigala reservoir catchment based on available digital data usingGIS.

River Mahaweli was dammed closer to MinepeAnicut to build Randenigala reservoir with the elevation of160 m to 240 m (7 8 to 7 14N and 80 48 to 80 49 E). The capacity is 861 MCM and catchmentcomprise of 448 km2 in the Kandy and Nuwara-Eliya districts. The elevation of the catchment ranges from240 m to 2500 m. Method of Horton and Strahler (1945) was used to rank the stream segments. The streamnumbers were entered into the table and other analyses based on the mathematical formulas. The resultsindicated that the catchment area was 448.9 km2, perimeter 111.24 km, mean slope 36.8, axial length 30.5km, basin width 14.72 km, form factor 0.48, compactness factor 1.48, circulatory ratio 0.46, elongation ratio0.78, orders of stream network indicated, 1315 of first orders, 314 of 2nd, 72 of 3rd, 15 of 4th, 3 of 5th, 1 of 6thand one seventh order stream. The stream frequency and drainage density were 3.83 (no. of streams /km2)and 2.43 (km/km2). Bifurcation ratio was 3.65 and length of overland flow was 0.21 km. These findings areuseful in determining the effect of catchment characteristics such as size, shape, slope of the catchment anddistribution of stream network.

KEYWORDS: Morphometric features, GIS, Catchment characteristics