Estimation of Groundwater Recharge under various land ... - RMZ

Estimation of Groundwater Recharge under various land covers in parts of ...185Geology and SoilsGeologically, the study area consists ofPre-Cambrian formations with gneissand intrusive granites (mostly alongthe coastal tracts and adjoining areastowards east). In the northern part ofthe study area basaltic rocks of UpperCretaceous age are seen. Soil is deepparticularly in coastal areas (few feetto few meters). Laterites are commonlyfound in coastal areas and plateau regionis covered by black soils, where asthe up-ghat region is characterized byboth red and mixed soils. By contrast,large areas along the coastal tracts ofNorth Kanara district, the parts of WesternGhat are severely degraded with laterite(Geologically Recent in age) inducedby natural climatic variability. Inthe plateau areas of the Western Ghats,deep forest soils rich in humus. Blacksoil is found locally, i.e. in areas havingelevation above 500–600 m. Generally,regions with heavy rainfall and dissectedtopography (slope varying between12–15 %) are devoid of black soil indicatingthat, climate, topography andlack of drainage are more importantthan nature of underlying rocks in theformation of black soil.The Karnataka Forest Department(KFD) has taken up various reforestationstrategies depending upon the stateof land degradation. The major speciesused for the afforestation activities areTeak and acacia ariculiformis.MethodologyRainfall AnalysisThe entire Uttara Kannada district hasbeen divided into three distinct regionsbased on the elevation. The three regionsare Coastal, Up-ghats and Plateau.The automatic raingauge stationscovered under coastal region are, Kumta,Aversa and Bhatkal. Sirsi, Yellapur,Joida and Siddapur are included underthe Up-ghat region. Raingauge stationsavailable in the plateau region areMundgod, Dharma, Barchi, Bachanikiand Haliyal. The rainfall intensity andduration data for these rainfall stationswere extracted from the hourly rainfallcharts (The Water Resources DevelopmentOrganisation, Govt. of Karnataka,maintains these stations). Therecords from the raingauge stations ineach region were taken together to giveregional record totals in station years.This amalgamation of annual maximumvalues assumes that they are independentof the stations and they arerepresentative of their regions definedfrom the criteria. These compoundedrecords were then subjected to an analysisusing the Gumbel’s frequency distributionwith the probability weightedmoment method.As the first step of the analysis, the valuesof maximum intensities for 1 h, 2h, 3 h and 5 h duration from all 12 stationswere considered. The frequenciesRMZ-M&G 2010, 57