Baseline Report Yala and Nzoia River Basins
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Lower YalaThe Lower Yala block is located in Kisumu and Siaya Districts. The block contains twelve sub-locations. This block is characterized by low to medium gradient hills, with shallow depressions and small permanent streams. The Yala River traverseds the block from northeast to southwest. The population is largely Luo, but there are areas where Luhya predominate. The area is largely subsistence farming today with a mix of crops typical of the lower elevations of western Kenya. Maize and sorghum are the major crops; banana and cassava are also grown. The area is also an important producer of mangos. 
Figure 3.1. Administrative map of the Lower Yala block. The blue dots are the sampling points for the biophysical survey.
The area Lower Yala is generally characterized by moderate to steeply sloping terrain with slopes ranging between 1 and 35%. The northern part of the block has a few large hills, notably Nguge Hill in the northwest corner of the block (Figure 3.2). The central and southern parts of the block have a rolling terrain. The Yala River traverses the block from the northeast to the west. The block is dissected by a number of important tributaries of the Yala, including the Ogommo Nyanyo and the Dhoneno Rivers. Around 35% of block area is flat with slopes of less than 5% (Table 3.1). Moderate to steep slopes (> 10%) cover 22% of the block. The areas around clusters 4, 12 and 16 are more hilly, with slopes exceeding 10%. The eastern part of the block also has more sloping land with 30 to 40 percent of the plots in clusters 14 and 15 exceeding 10% slope. Cluster 8, between clusters 4 and 12 fellfall on the Yala River flood plain in Uriri sub-locations. 
Figure 3.2. Topographic map of the Lower Yala block showing streams, and rivers, and rndomized sampling points Table 3.1. Average slope, slope range and incidence of steep slopes
The soil texture in this area is mainly clay loam (Table 3.2). The soils of the eastern part of the block are somewhat lighter textured than the western part of the block, with a higher presence of sandy and slitysilty clay loam soils. Clay soils were associated predominantly with mid-slope sites and some bottomlands. Table 3.2. Soil texture (% of samples).
Soil depth restrictions were widespread across the block, with 39% of the subplots sampled showing restrictions within the first 50 cm and 20% of the subplots showing restrictions within the first 20 cm. Clusters 1, 2, 11 and 14 had very high incidence of depth restriction. Clusters 3, 13 and 15 had relatively low incidence of depth restrictions. Table 3.3. Incidence of depth restrictions per cluster (values = % of subplots per cluster with depth restrictions; n = 40).
Farming is the major land-use and drives land cover in the block (Table 3.4; Figure 3.3). Agriculture is dominated by cereal production, but there are also areas with perennial grasses for livestock grazing. There are small areas of woodland along the Yala River. Much of the land around Cluster 5 is fallow or abandoned scrub land. The project should look closely at this area for rehabilitation. The second most common vegetation type was grasslands. Natural grass species includes both perennial and annual both palatable and unpalatable for livestock. The dominant species in the area are:
Table 3.4. Land cover classification (N=160??)
Figure 3.3 Land use in Lower Nzoia Blockk. The largest allocation of land in this block was for grazing livestock. The area used for food production was somewhat less. Notably, food production was largely absent in clusters 4 and 11, but grazing was the dominant land use in these clusters. A small percentage of the land was used primarily for producing wood. A classification of the primary current land use showed the following: Food / beverage: 43% Forage: 55% Timber / fuel wood: 12% Other: 4% In general there are few trees in the landscape. No woodlots or planted plantations were found during the survey. Of the 160 plots sampled only 28% or 45 plots had trees in the vicinity. This woody vegetation is mostly broadleaf and evergreen, (Table 3.4). The woody vegetation present in this area is broadleaf and evergreen. Markhamia lutea was the tree most commonly encountered. Terminalia brownii, Psidium guajava and Senna spectabilis were also commonly seen. There was a wide variety of shrubs encountered including Rhus vulgaris, R.hus natalensis, Lantana camara, Carissa indulis and Tithonia diversifolia. Shrubs were widely present in the landscape and were measured on 82% of the plots. Few exotics trees were found on the plots sampled. Ipomea spp. was widespread in this block indicating low soil fertility. Table 3.4. Wood vegetation type (% of plots with vegetation types present)
In this block all farms surveyed are privately owned and for 28% of the plots land use has not changed since 1990. However it was impossible to ascertain whether land use has changed for the majority of the plots (59%).
Soil erosion was visible in 57% of the plots, with highest incidence in clusters 1, 4, and 6. Because of the presence of sodic soils on the lake plains in this block, presence of erosion does not always correspond with steep slopes. Clusters 10, 11 and 16 had the lowest incidence of soil erosion. The principal type of erosion is mainly sheet erosion, but rill erosion was more common in this block than what has been seen in other blocks of the Yala River basin (especially clusters 4 and 11). Table 3.5 indicates on a cluster basis, the percentage of points showing visible signs of erosion. Soil and water conservation is practiced in this block, but needs to be expanded. The clusters with the highest incidence of erosion were not the areas where most of the erosion control structures were encountered. Nevertheless, soil conservation structures were found in all but three clusters within the block. Therefore, the project can build on current practices and extend soil and water conservation practices. This should be done in association with tree planting and should be one of the first activities undertaken in this block. Table 3.5. Percent of plots showing erosion features for each cluster
Table 3.6 Summary of baseline parameters
* Low: <15%; Moderate: 15 to 65%, High: > 65%. |