LAND DEGRADATION MONITORING PROGRAMME OF THE NATIONAL ENVIRONlMENT AND HUMAN SETTLEMENTS SECRETARIAT MINISTRY OF ENVIRONMENT AND NATURAL RESOURCES KIAMBU DISTRICT, T KENYA HE FIRST PILOT STUDY (Preliminary Report) Laurence A. Lewis Clark University/NEHSS with assistance 7r)m G. Kamau/NEHSS aid R.C. Cheruiyot/NEHSS September, 1982 Funded by the U.S. Agency for International Development, ETMA Program (AID/afr-C-1697) and The Government of Kenya OBJECTIVES This pilot study, begun in July, 1981, is the first stage in developing a methodology to provide basic information on soil erosion to planners, district officials and operating ministries in Kenya. The results of this programme will provide some of the crucial environmental data that will help NES to exe­ cute its mandate to monitor the state of the national environment. The speci­ fic objectives of the Erosional Monitoring Programme are to: - develop a methodology that can rapidly be applied and used in the diverse environmental settings found throughout Kenya; - quantify the amount of erosion occurring in rural areas; - identify the general rural environmental settings in which erosion is a major problem; - develop a simulation technique to determine if proposed activities will be deleterious to the existing land resource base, and, if so, what changes in land use plans might be suggested to minimize negative impact; and, - this should help the NEHSS to suggest priorities for remedial action and appropriate strategies to use. As one intent of the Secretariat is to make this infcrmation available to any ministry concerned with ameliorating land degradation; the data provided will be in a format that can be utilized in designing general safe criteria for land use planning as well as for legislative purposes. Personnel and Governmental Organizations Involved in the Pilot Study The success of the pilot study required the cooperation of numerous organizations and individuals that had first-hand experience and knowledge of the soil erosion situation within Kiambu District. No matter where future 1 monitoring programs will occur in Kenya, the need exists to obtain the crucial cooperation of the individuals living and working in the area if information is to be rapidly and accurately gathered. Several individuals cooperated with this project and insured its success. Particular appreciation is given to Mr. P.M. N'jenga who acted as liaison with Ministry of Agriculture personnel in Kiambu District and assisted this project continuously throughout the field portion of this project. The following were particularly helpful : Mr. Kobia ­ formerly District Commissioner Kiambu District (now Western Province) P.C. and the seven district officers in Kiambu District Mr. Kibage - District Agricultural Mr. Office P.M. N'jenga - Kiambu Crop Specialist, District Office Kiambu Divisional Extension Agricultural Officers - Mr. Stephen K. Ng'ososei (Gatundu) Mr. K.C. N'getich (Githunguri) Mr. H.P. Obade (Kiambaa) Mrs. G.N. Maingi (Kikuyu) Miss G.W. Kamakia (Lari) Mr. Keinduiwa (Limuru) Miss Amenya (Limuru) Mr. J.M. Karanja (Thika) Dr. Lawrence Ulsaker - Kenyan Agricultural Research Institute allowed NES to utilize the laboratory facilities to dry and weigh the soil samples Almost all of the farmers interviewed in Kiambu were very much concerned with the problem of soil loss and realize the need to minimize it. I. the whole District, no farmer was ever unwilling to cooperate with the project. In particular, the following farmers need to be mentioned as they both permit­ ted measurements of soil loss to be made on their farms and watched the equip­ ment placed on their farms. In addition, they provided us with numerous agri­ cultural insights on the environmental problems affecting their farms and how they deal with them. Mr. Hiuhi; Mr. F. Gichuki; Mr. C. Njiriri; A'r. R. Kangeth; Mr. P.K. Kinundu; Mr. Njenda; Mrs. P.M. Gachigua; Mr. N. Kinyita; Mr. P. Kimani and Mr. G. Gichuki; Mrs. T.W. Kago; Mr. K. Mugatha; Mr. K. Njugunaj; Mr. R. Mwithuria. 2 Data Collection Approach Kiambu District, Central Province was chosen as the first pilot area. Data gathered in this pilot study are aimed primarily at developing the meth­ odology to permit NEHSS to rapidly assess existing and potential land degrada­ tion throughout the nation. Kiambu has many advantages for this initial inquiry. First there are a diverse number of physical environmental settings found within the district ranging from humid to almost semi-arid; flat to extremely steep; and rich volcanic highly resistant soils to poor clay highly erodable soils. In addition there are diverse human-economic situations rang­ ing from large estates to small individual farms less than 1/8 of an acre in extent; part-time and full-time commercial and subsistence farms; farms large­ ly export oriented to farms oriented to the domestic market including the Nairobi market; nonirrigated and irrigated farms; farms long established and farms in newly settled areas some of which are largely unplanned and others which are in government developed schemes. Finally the proximity of Kiambu to Nairobi minimizes the logistic problems during the first year when unexpected problems should occur in greater frequency than in future years. Littie soil erosional data were available at the onset of this study. Given the relatively weak data base for soil loss throughout Kenya, one cri­ tical need for this study is to develop a rapid approach that can evaluate soil loss in a resource context within the constraints of the Kenyan situa­ tion. This is crucial if the objectives of this study are to be met and information is to be made available to farmers. The strategy decided upon to evaluate the soil resource for Kiambu was to first simulate soil loss for the whole district under 'natural' vegetation conditions. The justification for this approach is that this is the condition under which the soils formed. This simulated soil loss is assumed to approximate the normal or geologic 3 erosion and represents a non-degrading soil condition under natural condi­ tions. The simulated values are assumed to be the minimal soil loss values possible. A major purpose of this study is to apply the methodology being developed to determine if soil degradation exists in Kiambu, and if so, its magnitude and areai extent. Thus it is necessary to compare actual soil loss (data collected in the field) with the simulated 'natural' soil loss. As the ratio between actual soil loss to the 'natural' soil loss increases, degradation increases. Areas where large ratio values exist are potential problem areas in terms of high soil loss for agricultural purposes and high sediment produc­ tion for that could limit projects. The assessment of 'natural' soil loss for Kiambu District was completed December, 1981. This information is available at the Natural Resources Division National Environment and Human Settlements Secretariat (Nairobi) and Internation Development Program, Clark University (Worcester). The assessment of actual soil loss took place over a six month period from January to July, 1982. The initial phase of the assessment was a reconnaissance of the district to determine the agro/economic settings found in the area as well as to observe the obvious soil erosion and conservation practices. The purpose of the reconnaissance was to insure that each (f Kiambu's major environmental settings would be included in the sample-of soil loss measurements during the 1982 long rains. In each of the seven divisions, a divisional agricultural officer, and often a D.O. and district agricultural officer accompanied NEHSS personnel on the initial erosion survey. The com­ plete spectrum of conditions ranging from major problem areas to well managed areas from their perspectives were examined. Conversations with the farmers and landowners added insights into reasons for crop selection, conserv,,tion 4 practices and other factors affecting land utilization. During this phase vegetation types (including crops) and location, topography, qully location and conservation practices were noted. The next phase of the investigation was the ir,.tallation of equipment to measure soil loss in the diverse settings found in Kiambu to determine their relations to environmental conditions. Beginning in the middle of February four automatic recording raingages were installed; one in Lari, Kikuyu, Kiambu and Gatundu Divisions. These gages measure both the quantity and i,,tensity of precipitation. In addition, data from the existing raingage at KARl was made available for our use. After the completion of raingage instal­ lation, 27 soil traps were placed in individual fields that constitute a sample of the environmental conditions found throughout Kiambu. At the end of March, the rains began. Precipitation data and soil loss data for the whole 1982 rainy season from the 29th of March to 30th of June were continuously collected and recorded. In addition 5 soil samples were sent to N.V. Philips in Allmelo, Netherlands to determine the major mineral properties of the soils found in Kiambu in order to approximate the erodabil­ ity of the soils. Simultaneous with the measurement of soil loss, all the major gullies found in the district were measured and the environmental situa­ tion in which the gullies were situated was noted. These measurements were done by both NEHSS personnel and the division agricultural officers. With the cessation of the rains, the analysis of the data began. 5 DATA ANALYSIS Four types of soil erosion were identified in Kiambu District during the pilot study. These are: soil loss (sheet wash) resulting from agricultural activities; gully erosion resulting largely from runoff of roads; erosion resulting from small individual quarry operations; and massive hillslope fail­ ure resulting from tree clearing on very steep slopes and tea/agricultural crop substitutions. While the primary focis of this study is on soil loss resulting from agricultural activities, the other three types of erosion are briefly discussed since they all affect the soil resource.