Integration Of Runoff Harvesting To Enhance Vegetable Cultivation For Nyakivogera Marshland In Ruhango District

Abstract

During the rain period, high discharge of water in marshland caused by uncontrolled runoff from the catchment causes floods lead to the reduction of agricultural command area which decreases the crop production and leads to unemployment for farmers, malnutrition and hunger. At other hand, in dry period, the marshland does not produce optimally due to lack of water to supplement the natural moisture. The harvesting of the water will permit the cultivation in all three agricultural seasons.

In this project, the rainfall data from METEO- RWANDA were used for getting the rainfall intensity in the catchment. The experiment such as geotechnical test was done for hydraulic structures stability; the topographic survey was done for getting the catchment area and slope of channel which will be needed in the hydraulic design.   The use of combined data helped to get the durable solution of the flooding in the marshland and provided effective irrigation in the marshland. Rainfall considered in design were calculated by considering rainfall data of the past 40 years and dependability of 50%. By using a tabulated data representation method, the required dependable annually average rainfall value was found at 20th year which is 1228.5mm.

The area of the catchment: Delineation of catchment was done using the Arc GIS, the outlet was taken at the end of channel with the coordinates (Longitude: 29.795 o, Latitude: -2.216 o) and the catchment area was found to be 38.68 hectares. According to the characteristic of watershed where the soil is sand, the slope is 15.3%, and vegetable cover, the runoff coefficient was 0.58 and runoff volume calculated by using rational equation 275,606.604m3 (inflows per year).

By considering that the water requirement of pepper selected as suitable crop in the marshland for 10hactares, by considering water evaporation and that the agriculture will be done in all three seasons of the year by using the Peak sequent method, the minimum capacity requirement of the reservoir was calculated to be 17300 cum. For the safety of slope issues the allowable height is 11.4m. After the design, the reservoir has height of 7m, bottom width of 30m and bottom length of 60m.