Rainfall-Runoff Analysis of a Compacted Area
Ongoing droughts and water scarcity problems indicate the significance of conservation of natural water resources. Rainwater harvesting is going to be the most applicable method to eliminate water scarcity and to meet the escalating demand. Hydrological analysis is unavoidable in any water harvesting structural designing. A study was conducted to analyze the rainfall-runoff characteristics by selecting an area of 1.23 ha as the study area, where prominent runoff occurred during the rainy season. Runoff for seven storms were measured using a rectangular notch and a relation between discharge and corresponding head for the notch at the downstream end of the study area was calculated. The R2 value obtained was 0.98 and the runoff coefficient for the study area was 0.12. Unit hydrograph from various storm hydrographs were derived and the unit hydrograph for the storms P1 and P7 were considered for the derivation of representative unit hydrograph for the studied area. A relation between rainfall and runoff was found out as Y = 0.201X - 0.8467 and the R2 value was 0.98. From rainfall mass curve analysis, a relation between maximum intensity and duration was obtained as Y = 9.0029X -0.6986. The R2 value was 0.95. The results showed that the rainwater recharge structures constructed based on the rainfall-runoff analyses in the study area enhanced the water table level. The derived rainfall-runoff relation and representative unit hydrograph will be helpful at any time to design the rainwater harvesting and recharge structures in the studied area.
Keywords: Water scarcity, rainwater harvesting, hydrological analysis, unit hydrograph