Design of Staggered Trenches for a Hard laterite Terrain and its Positioning using Geographic Coordinates

Abstract

Rain water harvesting is the technology used for collecting and storing of rainwater from land surface, rock catchment and roof using simple or complex technique. Contour and staggered trenches are cheapest methods of runoff harvesting and ground water recharge. They also help in retaining moisture on and near the ground surface thereby enabling establishment of vegetation . Thus it helps in improving the wastelands into productive ones. The present study was conducted in Chelloor region of Kuttippuram gramapanchayat during the period of January 2005 to January 2006. the main objectives of the study were to conduct field topographic survey, calculation of runoff, design of staggered trenches and its positioning using geographic co-ordinates. The procedure followed, involved the calculation of the runoff potential of the area for the year 2005, measurement of infiltration capacity of the soil on the surface and after a little excavation, design of staggered trenches so as to harvest a fixed percentage of the runoff, and positioning of thr trenches using geographic co-ordinates. The results of the study revealed that the hill top of Chelloor is having a catchment area of 4.69 ha with high runoff potential. The infiltration capacity of lower layers of soil was found to be higher than the undisturbed soil surface. Staggered trenches 3m x 40cmx 30 cm spaced 3m between trenches and 5.5m between rows can harvest almost 50 % of the runoffoccurring from the area ( water conservation efficiency of 48.2 % is obtained based on runoff data for the year 2005). The positioning of the trenches can be much easily done than other conventional methods using GIS and GPS.