Estimation of Surface Runoff of Machhu Dam - III Chatchment Area, Morbi, Gujarat, India, using Curve Number Method and GIS

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1 IJSRD - International Journal for Scientific Research & Development Vol. 3, Issue 03, 2015 ISSN (online): Estimation of Surface Runoff of Machhu Dam - III Chatchment Area, Morbi, Gujarat, India, using Curve Number Method and GIS Jaysukh C. Songara 1 H.T. Kadivar 2 N. M. Joshipura 3 Dr. Indra Prakash 4 1 Student 2 Lecturer 3 Assistant Professor 4 Faculty 1,3 L.E. College, Morbi, India 2 Govt. Polytechnic Bhuj 4 BISAG, Gandhinagar Abstract Machhu River is one of the major North s flowing river of Saurashtra regions in Gujarat state. The catchment area of Machhu III lies in Machhu River Basin in Morbi taluka of Rajkot district. This catchment area falls under the category of sub watershed as per the size (24212 hectare) and thus curve number method has been applied for estimating runoff using GIS technology. The Curve Number (CN) has been estimated for Machhu Dam III drainage basin using a combination of land use (Crop land, Fallow land, Lakes / Ponds, Land with Scrub, Land without Scrub, Industrial Waste, Prosophis, Reservoirs, River, Towns/cities (Urban), Villages (Rural)),Soil (Fine Sand, Clayey), and Antecedent Soil Moisture Condition (AMC). Within this catchment number of land cover type and soil type exist. The original soil type map has been converted to a map of Hydrologic Soil Groups (HSG) using the published conversions. Weighted area curve number has been determined in order to find a representative curve number by integrating attributes of various thematic layers in arc GIS using the areas of the different land cover and soil types as weighting factor Key words: GIS, Curve Number (CN), Hydrologic Soil Groups (HSG), Antecedent Soil Moisture Condition (AMC) catchment (24212 hectare). This method is presently being used widely for the calculation of runoff. II. HYDROLOGY OF THE AREA Hydrological parameters help in quantification of water available in the catchment area. Hydrology of watershed determines the location and design of hydrological structures and development of watershed. The average annual rainfall in the Machhu basin is 456.7mm. July is the month which rains most in the study area with 41 per cent of season s rainfall received during the month followed by August as shown in Fig.1 about 96 per cent annual rainfall is received during rainy season. I. INTRODUCTION Machhu River is one of the North s flowing rivers of Saurashtra region in Gujarat state flowing through districts of Rajkot and Surendranagar. Machhu river originates from the hill ranges of Jasdan Sardar and Mandva in Rajkot district and Chotila in Surendranagar district and flows in north westerly direction along the district boundary of surendranagar and Rajkot up to village Beti and then flows mostly towards north in Rajkot district and finally disappears near Malia in little Rann of Kutch. To utilize river water for irrigation three dams have been constructed across the Machhu River namely Machhu Dam I, II & III. Machhu Dam I and Machhu II are already constructed and Machhu Dam III is in final stage of construction.the present study is being carried out in the catchment area of Dam III located about 2 km up stream of village-juna sadulka and 8k.m. downstream of Morbi city, Rajkot district. The catchment area of Machhu Dam-III is 2088 km2. This dam is being constructed mainly for irrigation. There are number of methods to find out runoff such as Rational Method, Green-Ampt Method, and SCS-CN Method. Rational method is mainly used for the estimation of the maximum discharge of catchment for small drainage area of up to about 200 acres (80 hectares) (K.R.Arora). The study carried out in Malaysia indicated that result of SCS-CN and Green-Ampt Method are same (AUTHOR). Whereas SCS- CN and Green Ampt methods are for the estimation of runoff for relatively large area. Therefore, SCS -CN method has been used in the present study considering size of the Fig. 1: Average Monthly Rainfalls over Last 20 Year ( ) In the Study Area III. CHARACTERISTIC OF CATCHMENT AREA The catchment area of Machhu III lies in Machhu river basin in Morbi taluka of Rajkot district. Machhu River is one of the major North flowing river of Saurashtra region in Gujarat state. The study area falls under Survey of India sheet number 41J16 between latitude & and longitude & Altitude of the catchment area varies between Elevations 27m and 96 m above mean sea level. This catchment area falls under the category of sub watershed as per the size ( hectare). Major part of catchment area is occupied by agriculture land where groundnut and cotton crops are being grown presently during monsoon. Wheat and cumin are also grown during winter season. The total area of the watershed is 241 km2. Two rainguage stations covers entire watershed namely Morbi and Machhu-II. All rights reserved by

2 Fig. 2: Location Map of Study Area IV. METHODOLOGY The methodology adopted for the present study includes: 1) Creation of thematic Maps (Land use map, Soils map, etc.) with the help of LISS-III, LISS IV and Cartosat images and using remote sensing and GIS. 2) Collection and integration of collateral Data such as Administrative boundary, State boundary, District Boundary, Taluka Boundary, Meteorological Data and Hydrological Data with the thematic layers. 3) Arc GIS software has been used for developing Hydrologic Soil Group map. Land use and Soil Characteristics of the area were used for calculation of Runoff by Curve Number method. 4) Synthesis and Analysis of data in conjunction with various thematic layers has been done to estimate of Surface Runoff in Machhu Catchment Area. V. SCS CURVE NUMBER METHOD In the early 1950s, the United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) (then named the Soil Conservation Service (SCS) developed a method for estimating runoff from rainfall. This method also referred as the CN method. Fig. 3: Methodology The SCS curve number method is based on the water balance equation & two fundamental hypotheses which are stated as, 1).ratio of the actual direct runoff to the potential runoff is equal to the ratio of the actual infiltration to the potential infiltration, and 2).the amount of initial abstraction is some fraction of the potential infiltration. (Handbook of Hydrology, 1972). (1) F = (P - Ia) - Q (2) Substituting eq. (2) in eq. (1) and by solving; Where, Q = actual runoff (mm), P = rainfall (mm), Ia = initial abstraction, which represents all the losses before the runoff begins and is given by the empirical equation. Ia = 0.2 S (4) Substituting eq. (4) in eq. (3); the eq. (3) becomes (3) For P>Ia (0.2S (5) S = the potential infiltration after the runoff begins given by following equation. (6) The CN (dimensionless number ranging from 0 to 100) is determined from a table, based on land-cover, HSG, and All rights reserved by

3 AMC. HSG is expressed in terms of four groups (A, B, C, D) according to the soil s infiltration rate. AMC is expressed in three levels (I, II and III), according to rainfall limits for dormant and growing seasons. CN value was adopted from Technical release (TR-55).Although, SCS method is originally designed for use in watersheds of 15 km 2, and it has been modified for application to larger watersheds by weighing curve numbers with respect to Watershed/land cover area. Equation of Weighted Curve Number is Given Below. (7) Where CN w is the weighted curve number; CN i is the curve number from 1 to any number N; A i is the area with curve number CN i ; and A the total area of the watershed. Steps for Estimation of Runoff using SCS-CN Model The following procedure was used to calculate the surface runoff: 1) Deciding the antecedent moisture condition(amc- II)as describe above. 2) Preparation of Land Use/Land Cover (Fig.4) & Soil map(fig.5) using satellite images. 3) Preparation of the Hydrological soil Group layer from available soil map as shown in (Fig. 6) 4) Integrating HSG and LU/LC maps in GIS environment and estimate CN (Table-3) 5) Calculation potential maximum retention (S) using Eqn.6 & Initial Abstraction(Ia) using Eq.4 6) Calculation of daily, Monthly & Annually runoff using Eqn.5. AMC Group Soil Characteristics In Present study Average Rainfall and Average Runoff for the period of (2010) shows in Fig. 8 VI. ANTACEDENT SOIL MOISTURE CONDITION(AMC) Antecedent Moisture Condition (AMC) refers to the water content present in the soil at a given time. It is very important factor for determine Final CN value. SCS developed three antecedent soil-moisture conditions and labeled them as I, II, III, according to soil conditions and rainfall limits for dormant and growing seasons. Classification of Antecedent Moisture Condition is shown in Table 1.In Present Study Average condition (AMC-II) is taken for Determine CN value for Machhu Watershed. Sr.No Land use Hydrologic Soil Group A B C D 1 Crop land Lack/pond Industrial waste Urban Village Land with scrub Land without scrub Fallow land River Reservoir Prosophis Table 1: Runoff Curve Numbers (AMC II) for Hydrologic Soil Covers (Ref-TR 55(1986) Total 5 day Antacedent rainfall(mm) Dormant Growing Season Season 1 Soils are dry not to wilting point,cultivation has taken place <13 <36 2 Average Condition Heavy or light Rainfall and low temperatures have occurred within the last >28 >53 5 days;saturated soils Table 2: Classification of Antacedent Soil Moisture Condition AMC VII. THEMATIC MAPS USED IN THE PRESENT STUDY A. Land Use Map: Land use depends on the natural and anthropogenic activities. These maps have been developed using Envy and Arc GIS software. In the catchment area Crop land, Fallow land, Lakes / Ponds, Land with Scrub, Land without Scrub, Industrial Waste, Prosophis, Reservoirs, River, Towns/cities (Urban), Villages (Rural) have been identified and delineated (Fig.2). B. Soil Map: Two types of soils have been identified in the area. Statistical analysis of the area with the help of Arc GIS has been done which gave the values for fine sand as 42.40% and Clayey 40.71% (Fig.5). Fig. 4: Land use Map All rights reserved by

4 VIII. HYDROLOGIC SOIL GROUP CONDITION (HSG) SCS developed soil classification system that consists of four groups, which are identified as A, B, C, D according to their minimum infiltration rate. Table 2 shows the hydrological soil group classification. CN values were determined from hydrological soil group and antecedent moisture conditions of the watershed. The Curve Number values for AMC-I and AMC-III were obtained from AMC-II (Chow et al. 1988) by the method of conservation. Runoff curve numbers (AMC II) for hydrologic soil cover Complex are shown in Table III &Fig. 6 shows the HSG map & Fig.7 shows the CN map of Machhu River Watersheds. Fig. 5: Soil Map Sr.No HSG SoilTextures A B Deep,well drained Soils Moderately Deep,well drained with moderately fine to coarse textures Sand, Loamy sand or sandy loam Runoff Potential Minimum Rate of Infiltration (mm/hr) Low Silt loam or loam Moderate C Moderately Fine to Fine textures Sandy Clay loam Moderate Water Transmission High rate (0.30 in/hr) Moderate rate ( in/hr) Low rate ( in/hr) D Soil which swell significantly when wet,heavy plastic and soil with a permanent high water table Clay loam,silty Clay loam,sandy Clay,Silty Clay,Clay High Very Low rate ( in/hr) A. Preparation of Hydrologic Soil Group Map: Soil classification system developed by SCS-CN has been followed while classifying soils into different hydrologic soil groups. In this classification system, soils are classified as A, B, C or D hydrologic soil group depending on their properties. Category A soil has lowest runoff potential whereas category D soil has highest runoff potential Hydrologic soil group map of the study area having 2 classes of soil as fine loamy, clayey loamy shown Fig: Category C has given to fine loamy class, and category D has given to clayey loamy. Table 3: USDA-SCS Soil Classification Fig. 6: HSG Map B. Weighted Area Curve Number: Different layers of landuse/land Cover, Soil, HSG were added in Attribute table was using ArcGIS 9.3.Byusing Tool box Union of the above layers are prepared.the result obtained from union attribute was used to compute Weighted area curve Number of the study area. Sr.No. Different Classes Soil Type HSG % Area CN A*CN Weighted Curve Number(WCN) 1 Crop land Fine C Clayey D Fallow land Fine C Clayey D Lakes / Ponds Fine C All rights reserved by

5 Clayey D Land with Scrub Fine C Clayey D Land without Scrub Fine C Clayey D Mine Dumps / Industrial Waste Fine C Clayey D Prosophis Fine C Clayey D Reservoirs Fine C Clayey D River Fine C Clayey D Towns/cities (Urban) Fine C Clayey D Villages (Rural) Fine C Clayey D Table 4: Calculation of Weighted Curve Number for AMC II Fig. 9: Daily Rainfall-Runoff-Infiltration Fig. 7: Curve Number Map IX. CALCULATION RUNOFF USING SCS METHOD Available rain fall data from the yaer 1991 to 2010 has been evaluated. However, for the present study data of the year 2010 has been used for the calculation of runoff ( using Equation 5). In this year maximum rainfall was observed during the period As per callculation potential maximum retention (S) is and initial abstraction (Ia) is in the year X. CONCLUSIONS Catchment area of Machhu III dam comes under sub catchment of Main Machhu River Basin. Size of the sub catchment area is about hectare. SCS-CN method has been used for the calculation of this sub catchment/ watershed in GIS environment. For this data various thematic layers such as Land Use, Slope, Soil and hydrology has been synthesized and analyzed for the classification of HSG Group (C and D type) and for obtaining Curve Number (82.85). Estimated runoff using SCS-CN method can be used for the effective watershed management in conjunction with GIS study. XI. ACKNOWLEDGEMENTS We are thankful to the Director, Bhaskaracharya Institute for Space Applications and Geoinformatics (BISAG), Gandhinagar and Head of the Department of Civil Engineering, L.E. College-Morbi for providing facilities and encouragement in conducting research in the Water Resources Engineering. We are also thankful to Mr. Khalid Mahmood, Project Manager and technical staff of BISAG for helping in laboratory work. Fig. 8: Monthly Rainfall Vs Monthly Runoff REFERENCES [1] Ghanshyam Das Hydrology & Soil Conservation Eng. Prentice Hall of India, New Delhi, 2000): All rights reserved by

6 [2] Handbook of Hydrology (1972),Soil Conservation Department, New Delhi [3] JVS Murthy Watershed Management NEW AGE,SECOND EDITION (pg.21-34). [4] Pramod Kumar, K.N.Tiwari, D.K.Pal, Established SCS Runoff curve number from IRS digital data base journal of Indian Society of Remote Sensing vol.19,no.4,1991 [5] Tejram Nayak, Verma M.K, Hema Bindu.S, SCS curve number method in Narmada basin, International Journal of Geometrics and Geosciences Volume 3, No 1, 2012 [6] Technical Release-55 Manually, 1986 [7] K.R.Arora Irrigation, Water Power and water Resources Engineering Standard Publishers Distributors,(pg [8] Analysis of Surface runoff from Yerala River Basin using SCS-CN and GIS, International journal of Geomatics and Geosciences Vol 4, No 3, 2014 All rights reserved by