Supervisors : Mr. S. Matara Mrs. Tabitha Njoroge Title: use of gis in rainwater harvesting Name : otieno kerubo m faith reg. no. :f19/1454/2010 Supervisors : Mr. S. Matara Mrs. Tabitha Njoroge

Outline Problem statement Objectives Background What is rainwater harvesting? Progress and Way forward

PROBLEM STATEMENT Water is one of the basic necessities of life that are required daily. Without it life would not be the same. Some daily activities would come to a halt. The resource, water should therefore be available at all times. In arid and semi arid areas, this is just a mirage. This study seeks to solve the situation by determining potential/suitable rainwater harvesting sites using GIS. The purpose of this project is therefore to map out these harvesting sites and provide the information, which can then be used by the responsible authorities to put these water harvesting systems into place. For this purpose, the combined effort of GIS analysis and field surveys can be used. This report describes the mapping by GIS (Geographic Information Systems), of the rainwater harvesting potential in Seme

OBJECTIVES Main Objective The main objective is to use GIS to map potential Rainwater Harvesting sites in Seme Sub-county, and thereby provide a tool for advocacy and decision support for RWH in the area. Specific Objectives To perform a review of water harvesting techniques (rooftop RWH, surface runoff into ponds, in-situ RWH) To prepare a GIS Geo-database of the surface water situation in Seme Sub-county To apply the geo-database in mapping potential RWH sites in Seme Sub-county  

background In the area of study, which is Seme sub-county, there is a big water problem since the area experiences erratic rainfall. The activities that take place in the area include agriculture, livestock rearing and other economic activities and daily activities that require water. When the rain falls in the rainy season, only a few people store the water in tanks since the area is largely rural and most people cannot afford water tanks let alone iron sheet roofs. Later on in the dry season, the water problem comes back and people have to walk long distances to get water and even spend a fortune on water, by buying from people with boreholes. It is because of this that I took up the challenge to help in solving the problem as the area has a lot of potential for rainwater harvesting.

Rainwater Harvesting Rainwater harvesting is the process of accumulation and storage of rainwater and runoff for re-use on site or away from the rainfall site using various technologies. The different technologies that could be used in doing this include: In situ Internal (micro) catchment RWH-the field is also the catchment area (CA is less than 1000m2) External (macro) catchment RWH-many fields share water trapped from a large catchment area(1000m2- 200ha). This project looks mainly at the macro catchment techniques.(plastic lined underground tanks, water pans, tanks,rock catchments).

Rainwater harvesting examples

Data needed and data collected The key factors that determine whether a site is suitable for rainwater harvesting are listed below: Information on precipitation in the area Population data, population density Topography data (contours from topographic map of the area) Data on Settlement Soil data(soil depth, soil pH, soil texture) Land use and land cover data Rivers and roads in the area

Methodology flowchart

Criteria for analysis Procedure for this project can be listed basically as stated below: Collecting datasets for input into the GIS model Assigning weights to each of the datasets Combining and analyzing the selected datasets. The analysis will be done using the following methods: Weighted overlay analysis Land cover data analysis Surface hydrology modeling Buffer analysis

PROGRESS AND WAY FORWARD Data acquisition Data editing DEM creation Data analysis which includes: Hydrological modeling Slope map creation (aspect map) Soil and Land cover data analysis (reclassification) Creating a Rainwater harvesting potential sites map

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