Cn Method in the Pambar River Basin, India
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IJREAS VOLUME 5, ISSUE 6 (June, 2015) (ISSN 2249-3905) International Journal of Research in Engineering and Applied Sciences (IMPACT FACTOR – 5.981) PRIORITIZATION OF WATERSHED THROUGH SURFACE RUNOFF IN PAMBAR RIVER BASIN USING SCS - CN METHOD IN THE PAMBAR RIVER BASIN, INDIA Baidyanath Kumar Research Scholar, Department of Geography B.R.A Bihar University, Muzaffarpur, Bihar Abstract A watershed is an area that drains water and other substances to a common outlet as concentrated drainage. Nowadays watershed management plays a vital role in water resources management. Watershed based on water resources management is necessary to plan and conserve the available resources. Remote Sensing (RS) and Geographic Information System (GIS) techniques can be effectively used to manage spatial and non spatial database that represent the hydrologic characteristics of the watershed use as realistically as possible. The present study has been conducted on Pambar River is one of the major river drains the eastern slopes of Western Ghats covering Anamalai – Cardamom hill ranges. The Pambar watershed basin receives the average annual rainfall of 43.7 inches mainly during June to September monsoon season (1961-2005). Sandy clay loam, Clay loam, silty clay loam, sandy clay, silty clay, or clay are the main soil group confined in this basin. Such a soil group obviously allows less water to infiltrate into it. The result runoff will be more. Due to high runoff potential and poor infiltration, drought like situation prevails in this area from December to June almost every year. So the conservation of watershed is very much essential to protect the environment. The watershed conservation priority number for the each watershed will be assigned according to the value generated from the runoff. Keywords: SCS – CN; Rainfall; Pambar; GIS; Remote Sensing 1. Introduction Watershed is defined as “ Natural hydrologic entity that cover a specific area expanse of land surface from which the rainfall runoff flows to a defined drain, channel, stream or river at any particular point” (K.V Seshagiri Rao, 2003). A watershed is made up of soil, vegetation and water along with the people and animals who are the integral part of the system (Sreedevi TK et al, 2004). Modeling of the event based rainfall runoff process has significant important in Hydrology (R K Sahu et.al, 2007 ) The CN is a hydrologic parameter used to describe the storm water runoff potential for drainage area. The CN is a function of land use, soil type, and soil moisture. (Jeffry Swingly Frans Sumarauw, 2012) The core focus of watershed management is controlling the flow of water and runoff material to the down slope areas, which is an applied and multidisciplinary subject based on geology, ecology, environmental economics and the social sciences (Food and Agriculture Organization of UN, 2006). A watershed is the area covering all the land contributes runoff water to a common point ( R. Amutha et al, 2009). Rainfall runoff is an important component contributing significantly to the hydrological cycle, design of hydrological structures and morphology of the drainage system. (Ratika Pradhan et al, 2010). Runoff refers to the flow of water from the land as both surface and subsurface discharge; the more restricted and common use, however, refers to runoff as surface discharge in the form of overland flow and channel flow. (William. Marsh et al, 2013). The relationship between rainfall runoff and annual spatial soil loss is determined using USDA Soil Conservation Service (SCS) method in conjunction with remote sensing and GIS technology (A S Jasrotia, 2002) The hydrological response of watershed is usually International Journal of Research in Engineering & Applied Sciences 159 Email:- [email protected], http://www.euroasiapub.org IJREAS VOLUME 5, ISSUE 6 (June, 2015) (ISSN 2249-3905) International Journal of Research in Engineering and Applied Sciences (IMPACT FACTOR – 5.981) altered due to revolution in the watershed development. Thus it is necessary to quantify the likely changes in the surface runoff in a watershed as an impact of the planned or unplanned changes made in the land use (Tejram Nayak, 2012) Watershed management implies proper usage of water to land and other natural resources in a watershed for estimation of runoff which is required for planning, developing and managing the water resources and irrigation scheduling. Runoff is one of the important hydrologic variables used in the water resources applications and management planning. For gauged watershed accuracy of estimation of runoff on land surface and rivers requires much time and effort. GIS is utilized as a tool to store analyse and integrate information pertaining to runoff, slope, drainage and fractures (D. Ramakrishnan et. Al Aug. 2009) In the present study SCS-CN technique was used to generate rainfall runoff model by incorporating spatial variation of the various physiographic characteristics of the study area such as geomorphology, geology, land use / land cover, soil and drainage pattern integrated with the help of Remote Sensing data and GIS techniques. 2. Study Area The present study has been conducted in Pambar River Basin situated in Devikulam Taluk, Idukki district of Kerala. Among the three east flowing rivers in Kerala, Pambar River is one which drains the eastern slopes of Western Ghats covering Anamalai – Cardamom hill ranges. The study area stretched between the latitudes of 1008’ 0’’ to 100 12’ 0’’ N and longitudes of 7703’0’’ to 77016’0’’E covers an area of about 289 Sq.Km. Pambar river basin is a 6th order basin developed in a part of the Proterozoic, high-grade, Southern Granulite Terrain of the Peninsular India are carved out of a terrain dominantly made of granite- and hornblende-biotite gneisses (S. Suresh et al, 2014). The study area has been divided into different geomorphic units, such as escarpments, valley fill, Highly dissected denudational slopes, valleys, denudational slope etc. It covers Keezhanthoor, Kanthalloor and parts of marayoor and Kannan Devan Hills Villages. Pambar River is one of the main tributaries of Chinnar River flowing from west to east confluence near Chinnar chauki settlement. Map.1 Shows the Study are a location. International Journal of Research in Engineering & Applied Sciences 160 Email:- [email protected], http://www.euroasiapub.org IJREAS VOLUME 5, ISSUE 6 (June, 2015) (ISSN 2249-3905) International Journal of Research in Engineering and Applied Sciences (IMPACT FACTOR – 5.981) Map 1: Study Area Location 3. Aims and Objectives The aim and objective of the present study is To calculate season wise runoff in a watershed To assign priority rank on the basis of runoff value 4. Data The Survey of India topographic maps no 58F03 & 58F04 and Google terrain map were used for the demarcation of the watershed boundary. Geological Survey of India (1:2,50,000) for Idukki District is used for geological map. The rainfall data of Pambar watershed basin from 1961 to 2005 have been used in the study. The rainfall data is collected from Munnar UPASI Idukki District. The land use and land cover map was prepared using Google satellite imagery of Pambar basin for the year 2013. The soil information was collected from the soil map of Idukki District, published by the Soil Survey Organization and Agriculture Department. To compute the runoff SCS-CN formulated by United States department of agriculture, 1986 has employed 4. Methodology All tributaries of different extents and patterns, Soil cover map, Geology map, Land use and land cover map were digitized from corresponding sources in ArcGIS 9.3 software platform. On the basis of rainfall availability, the rainfall data has divided into three categories. They are summer season (February – May), Monsoon season (June – September) and Winter season (October – January). Inorder to scrutinized the runoff in the Pambar river basin landuse – land cover and soil International Journal of Research in Engineering & Applied Sciences 161 Email:- [email protected], http://www.euroasiapub.org IJREAS VOLUME 5, ISSUE 6 (June, 2015) (ISSN 2249-3905) International Journal of Research in Engineering and Applied Sciences (IMPACT FACTOR – 5.981) layer have been merged together and the appropriate CN value was assign in the merged data as a separate field on the basis of soil and landuse and availability of rainfall in situ. Based on the runoff value the sub watershed basin has been arranged in hierarchy manner. Thus the final output has been evolved. 4.1 Curve Number (CN) Analysis The CN is estimated for a drainage basin using a combination of river basin, land use, soil (Jeffry Swingly Frans Sumarauw et.al, 2012). The CN generator requires three shape files the drainage basin boundaries for which CN will be calculated, the soil type, and the land use layer. The information needed to determine a CN is the hydrologic soil group (HSG), which indicates the amount of infiltration the soil will allow. There are four hydrologic soil groups (USDA, 1986). They are given below in Table-1. Table-2 presents the typical land use categories used for hydrologic analysis, along with corresponding curve numbers for each land use-soil group combination. Effect of Hydrologic Soil Group on Runoff Volumes and Peak Rates. HSG Soil Textures A Sand, loamy sand, or sandy loam B Silt loam or loam C Sandy clay loam D Clay loam, silty clay loam, sandy clay, silty clay, or clay Table 1: hydrologic soil groups Group A soils have low runoff potential and high infiltration rates even when thoroughly wetted. They consist chiefly of deep, well to excessively drained sand or gravel and have a high rate of water transmission (greater than 0.30 in/hr) Group B soils have moderate infiltration rates when thoroughly wetted and consist chiefly of moderately deep to deep, moderately well to well drained soils with moderately fine to moderately course textures.