Baseline Report Yala and Nzoia River Basins

Upper Yala

The Upper Yala block is located in Uasin Gishu District. The block contains nine sub-locations with Kesses and Tulwet sub-locations covering more than 80% of the block area (Figure 5.2). Lake Lessos is located in the centre of the block, and this lake is one of the main sources of Yala River. This block is characterized by medium gradient hills, shallow depressions, wetlands and flood plains with small permanent streams.
Before independence, white settlers were managing the land as grasslands with indigenous trees interspersed across the landscape and enclosed paddocks of improved pastures. Some areas were cropped towith wheat in a rotation system with other food crops. Today, the area is largely planted towith maize with grasslands interspersed. Only a small portion of the block is planted to wheat. There a few shrubs and trees seen in the landscape. Farms are very large in the area and there is little subsistence agriculture.




Figure 5.1. Administrative map of the Upper Yala block. The blue dots are the sampling points for the biophysical survey

2. Biophysical baseline data summary

   1. Topography

The area of Upper Yala is generally characterized by level terrain at a relative higher altitude: 2100-2400 meters above sea level with slopes ranging between 1 and 6% (Figure 5.2). More than 65% of block area is located on plains with 13% being located on plateaus (cluster 14 & 15) and medium gradient slopes. The area around cluster 9, 10 and 14 is more hilly, with slopes up to 10%. Shallow depressions constitute 8% of the landscape (cluster 1, 2, 9, 11, 12, 13 and 16).



Figure 5.2. Topographic map of the Upper Yala Block showing streams and roads.
The area around Lake Lessos, in the centre of the block, is characterized by wetlands and shallow depressions, with medium gradient hills located around cluster 3 and 13, which often floods. The table below lists average slope, slope range, and slope for point with slopes larger than 10%.
Table 5.1. Average slope, slope range and incidence of steep slopes .

Cluster	Average slope (%)	Slope range (%)	No, values > 10%
1	1.5	0.50 – 2.50	0.0
2	6.0	2.00 – 16.25	4.0
3	2.1	0.75 – 3.50	0.0
4	1.6	0.75 – 3.75	0.0
5	1.3	1.00 – 2.00	0.0
6	1.6	1.00 – 2.50	0.0
7	1.1	0.75 – 1.50	0.0
8	1.3	0.75 – 2.00	0.0
9	3.6	1.75 – 8.00	1.0
10	2.3	0.5 – 6.25	1.0
11	1.9	0.50 – 4.00	0.0
12	1.2	0.50 – 2.50	0.0
13	2.5	1.50 – 3.25	0.0
14	4.7	1.75 – 9.00	5.0
15	1.4	0.75 – 2.75	0.0
16	2.0	1.00 – 4.75	0.0

2. Soil texture and soil depth restrictions

The soil texture in this area is mainly silty clay to clay soils (Table 5.2). The remaining 5% of the sampled area is a mixture of clay and silty clay.
Table 5.2. Soil texture (percent of samples).

Silty clay	Clay	Silty clay	Sandy loam
74.3	24.6	0.5	0.5

Soil depth restrictions were not very apparent in this area. Only 11% of the sampled area showed soil depth restrictions, with the following clusters not experiencing any restrictions for the sampled areas: Clusters 1, 3, 4, 7, and 8. For the following clusters, less than 3 of the 10 sampled areas experienced depth restriction: Cluster 2, 5, 9, 10, 13 and 16. The only cluster which experienced depth restrictions in more than 60% of the sampled area is cluster 12.

3. Vegetation and land use

Farming is the major land-use and drives land cover in the block (Table 5.2). Agriculture is subsistence dominated by maize, beans, sorghum, and banana. TeaWheat is the major cash crop in the area. The block is also an important area for dairy production. 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 as follows:

8. 
   Setaria sphacelata: perennial grass; good forage;
   
9. 
   Sporobulus pyramidalis: annual grass; low forage value;
   
10. 
    Digitaria ciliaris: annual grass; low forage value;
    
11. 
    Digitara gazensis: perennial grass; high quality forage
    
12. 
    Eragrostis aspera: annual grass; moderate forage quality;
    
13. 
    Eragrostis superba: perennial grass; good quality forage;
    
14. 
    Hyparrhenia collina: perennial grass; good forage, but it should be stocked in the early stages of growth.
    

Other grass species are Cyperus ssp. which is dominant in swampy areas, while Sedge ssp. is a weed in cultivated areas.

Figure 5.3. Land use map of upper Yala Block .

Table 5.3. Land cover classification

Vegetation strata	No. points	Percentage
Farm land	76	48%
Forage land	16	10%
Perennial grassland	56	35%
Shrub land	1	<1%
Fallow	8	5%
Other	3	2%

A classification of the primary current land use showed the following

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 8% or 12 plots had trees in the vicinity. This woody vegetation is mostly broadleaf and evergreen, (Table 5.4).

Table 5.4. Wood vegetation type

Broadleaf	Needle leaf	Allophytic	Evergreen	Deciduous
19.4	0.0	0.0	16.3	0.6

The woody vegetation present in this area is broadleaf and evergreen. An assessment of the trees seen in the landscape showed the following species to be present: Acacia mearnsii, Eucalyptus spp., Pinus patula, Cuppresus incitanica, Grevillea robusta and Casuarina spp. These trees are mainly planted in the homestead and along farm boundaries. Most of the indigenous trees have disappeared from the landscape and are mainly found in small tickets on hill tops and sloping hillsides. These species include: Olea europea (Wild olive), Juniperus procera (African pencil cedar), Albizia gummifera, Cossonia holstii, Erythrina abyssinica (Red hot poker tree) and Dombeya goetzii with Acacia abyssinica being the dominant thorn tree in the area. However around cluster 14 indigenous trees are seen more frequently in the landscape.

Shrubby vegetation is present at all sampling plots, is less than 0.8m in height (87%) and is generally a mixture of annual and perennial types. The dominant indigenous shrubs are Clevendenron myricoides, Rhamus staddo, Rhus vulgaris, Carissa indulis and Vangueria acutiloba. These shrubs are mainly found in higher altitudes and in small thickets on hill tops and hill sides.
In this block all farms surveyed are privately owned and for 9% of the plots land use has not changed since 1990. However, for the majority of the plots, it is not know whether land use has changed or not (64%).

4. Soil erosion and conservation measures

Soil erosion was visible in 22% of the plots, with highest incidence in clusters 3, 8, 10 and 14, which corresponds well with average slope and slope range. Clusters 3, 10 and 14 have steeper slopes compared to the other clusters (up to 10%). The type of erosion is mainly sheet erosion with only one farm showing signs of rill erosion (cluster 2 plot 6). Table 5.5 indicates on a cluster basis, the percentage of points showing visible signs of sheet erosion.
Soil and water conservation is not being practiced in this block. Despite the presence of sheet erosion on 35 farms and steep slopes on several farms, none of the farms in the sample had established contour lines, terraces or other conservation measures to divert runoff and control soil erosion. Therefore, soil and water conservation in association with tree planting should be one of the first activities undertaken in this block.
Table 5.5. Percent of plots showing erosion in each cluster

Cluster	None	Sheet	Rill	Gulley
1	90	10	0	0
2	80	10	10	0
3	60	40	0	0
4	80	20	0	0
5	70	30	0	0
6	80	20	0	0
7	80	20	0	0
8	50	40	0	0
9	90	10	0	0
10	70	30	0	0
11	60	40	0	0
12	100	0	0	0
13	90	10	0	0
14	70	30	0	0
15	70	30	0	0
16	90	10	0	0