VOL. 4, NO. 3, MAY 2009 ISSN 1819-6608 ARPN Journal of Engineering and Applied Sciences © 2006-2009 Asian Research Publishing Network (ARPN). All rights reserved. www.arpnjournals.com ANALYSIS OF FLOW PATTERN BETWEEN HILL AND LAKE Devatha Chella 1 and Arun Kumar Thalla 2 1 Department of Civil Engineering, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand, India 2 Department of Environmental Engineering, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand, India E-Mail: revacp@gmail.com ABSTRACT The demand for water is increasing rapidly with the increased population, industries and irrigation which lead to the scarcity of water. In order to avoid such a scarcity, which will hamper the development of the country, water resources projects should be planned and managed effectively. The south part of the Chennai metropolitan in India consists of hills and lakes. Due to the rapid urbanization, all the lakes in this zone are being encroached thus hindering the contribution of lake for ground water resulting in the depletion of ground water. For this enhancing situation, a microlevel study has been carried out on the surface water estimation and analysis of sub-surface flow pattern. This paper mainly emphasize on ground water modeling using VISUAL MODFLOW. Groundwater flow models are used to calculate the rate and direction of movement of groundwater through aquifers. Estimation of surface runoff using Soil Conservation Service (SCS) shows that only in the year 2004, there is a high runoff which leads to over flow from the lakes and for the other years (2001- 2003) average runoff contribution to the lakes is from 17% to 45%. The ground water analysis was done for six years (2001 to 2006) and the results indicate that for the monsoon period the velocity ranges from 0.02 to 0.05m/sec and for the non-monsoon period it ranges from 3.21*10 -2 m/sec to 8.75*10 -2 m/sec. which implies that there is a rapid increase in the radius of influence due to urbanization. Keywords: model, ground water, flow pattern, modflow. INTRODUCTION The demand for water is increasing with the population, industries and irrigation leads to scarcity of water. In order to avoid such a scarcity it is important to improve the efficiency of the planning and management of water resources. Depletion of groundwater in areas where excessive withdrawals have occurred emphasizes the need for the analysis of the flow conditions. Just below the hill side groundwater mainly occurs in the unconsolidated weathered mantle, underlying fractures, fissures, joints etc. and are termed as hard rock regions. The weathered mantle is usually poorly permeable but has water storage capacity. The fractured zones have high transmissibility values depending on the course, upon the apertures and the interconnections of the fractures. Generally fractures are interconnected with weathered zone as a result groundwater in the weathered mantle may recharge the fractures. This shallow groundwater zone ends in a lake. Kirby (1988) defined the process of movement of water on the hill slope and its contribution to ground water as Hill slope Hydrology and classified the flow pattern in the hilly slopes as Hortonian overland flow, saturation overland flow and return flow. At any point on or below ground in a hilly terrain, water shall be moving under a combination of potential gradients viz by gravity and water pressure or tension. For a hill slope with uniform net rainfall, flow vectors are typically vertical through the soil. However, vertical flows are critical in a hill slope hydrology as they control the diversion of flow on the slopes that finally results in lateral flow. Reddi (1990) relates the fluctuation of the ground water on a hilly terrain as a function of rainfall intensity, evapotranspiration, flow in the unsaturated zone and drainage by gravity. Further, he developed a mathematical model for assessing the ground water level on hillside slopes by using two-dimensional finite differences method. Gupta and Singh (1985, 1988) did a comparative study between finite difference and mass balance model associated with partially penetrating well in a hard rock terrain for the simulation of flow regime and they concluded that Finite difference gives better results than a mass balance model. Kacimov (2000) describes the behavior of the lake, mainly its regime from gaining to losing, or flow through, as a function of the varying incident groundwater flow velocity, evaporation, precipitation runoff rates in the lakes and their hydrological characteristics. Yang et al (2002) proposed a flow-interval hill slope discretization scheme for catchment hydrological modeling. By this scheme, a two-dimensional catchment is simplified into a one-dimensional cascade of flow intervals linked by the main stream. This model performed well on simulating the overall water balance, general flow pattern, and daily and hourly hydrographs of a whole catchment, as well as simultaneous simulation in different sub catchments. Though many researchers have studied the surface and ground water balances, there has been limited study on the complex interaction of surface and ground water mass balances on a hilly slope. Generally more than 95% of water in the stream flow passes to into the ground before reaching the channel network. The fluctuation of groundwater levels depends upon many related process such as rainfall, evapotranspiration, flow in the unsaturated zone and drainage by gravity. With this as back ground, this paper mainly aims in (i) estimation of surface runoff of the study area using Soil Conservation Service (SCS) method (ii) analysis of 64