CS(AR)-1/2013 : Infiltration behaviour under various land use and its modeling in Mulsi river basin (Assam/Meghalaya)

Abstract

Prediction of overland flow in catchments depends on large extent on the characteristics of the infiltration process. An evaluation of the risk of overland flow is needed in order to minimize the risk of transferring pollutants from soil to rivers and lakes. The objectives of this study is the assessment of the infiltration capacity considering different land use and soil types in Kulsi River basin of North Eastern (NE) Region of India . In the present study, field infiltration tests were carried out using double ring cylinder infiltrometers under different soil-vegetation-land use complexes. Results were analyzed and typical infiltration rate and cumulative curves were developed for different land use and soil types. The results depicted large variation of infiltration rates depending upon various land use and soil type conditions. It was observed that steady infiltration rates decrease with respect to mixed dense forest, teak forest, tea garden, bamboo forest land, grassy & shrub land, barren and agricultural land. The overall variation in the steady infiltration rate for Kulsi River basin was found from 18.4 to 0.34 cm/hr. The present study shows that forest covers control the infiltration rates significantly in hilly areas. Extensive laboratory experiments were done on disturbed and undisturbed soil samples. Disturbed soil samples were used for textural and consistency analysis. Percentage of sand, silt and clays were determined through sieve analysis and hydrometer method. Different hydrologic, engineering, index and Atterberg's properties like moisture content, bulk density, dry density, sp. gravity, plastic limit, liquid limit, void ratio, saturated density, degree of saturation, uniformity coefficient, coefficient of curvature etc. were obtained for each soil sample. Grain size curves were plotted and particle size distribution ranges have been identified using USDA criteria. Textural classification was identified using triangular classification system of USDA. Permeability was also determined using ICW Lab Permeameter. Temperature and pH of soils under different representative land use conditions were also monitored. The overall variation of mean soil temperature in Kulsi River basin was found in the range of 20.5 to 24 °C whereas variation in soil pH ranges from 5.82 to 4.43 i.e. acidic in nature. Various popular infiltration rate loss models like Horton, Kostiakov, Green-Ampt, Philip, Holtan and Huggins-Monke were fitted with observed infiltration rate curves and evaluated using different statistical methods like regression coefficient, min. sum of square of relative errors and efficiency criteria. Parameters of these models were obtained using least square technique.