Overall seasonal energy cost analysis of smallholder pumped irrigation systems in the arid and semi-arid lands of Kenya

In Kenya, there has been a tremendous increase in the number of smallholder farmers using motorized pumps in their farming operations. The recent increase in uptake of pumps in irrigated agriculture is as a result of need to increase food production to meet the rising demand as well as modernize farming operations and has been met by various challenges. Among the challenges facing adoption of pumps is rising cost of energy particularly fuel used, diminishing energy reserves as well as lack of technical knowledge in selection, design and operation of these pumps. The result has been significant rise in cost of crop production in pumped irrigated agriculture. Combined with other factors such as market competition for agricultural produce and low market prices, the operation costs of smallholder pumped irrigated agriculture has as a result tremendously increased. The aim of this study was therefore to investigate the uptake rate as well as the cost of production due to pumps use in smallholder agriculture. This study was hence carried out in Kakuzi and Yatta divisions both located in the Arid and Semi Arid Lands and 80 smallholder farmers growing various horticultural crops such as French beans (Phaseolus vulgaris L), Tomatoes (Lycopersicon esculentum L) and Water melons (Citrullus lanatus) were considered. Face to face questionnaire as well as observational study was used to gather information. Detailed analysis of 10 pumps used in 10 sample farms was done to evaluate pumps working efficiency, fuel consumption rate and pumps water discharge under different operating conditions. This analysis helped in computing the overall seasonal energy cost of pumped irrigation. The study found out that despite the increase in cost of production as a result of pumping, farmers still adopted it with 80% of the studied population engaged in it. It emerged that high cost of fuel was the most limiting factor for 65% of the sampled population practicing pumped irrigation. Results indicated a big variation in fuel used to irrigate a unit piece of land from one farm setup to the other. In some farms growing similar crops, mean fuel (petrol) amount used to irrigate 1 hectare of land was in excess of 60L while in others, fuel used was as low as 5L. The overall seasonal energy cost in nearly all the farms investigated was over 50% of the total cost of production. The high value for overall seasonal energy cost could be attributed to several factors such as pump operating efficiency, fuel consumption rate and farm operating conditions (elevation, water conveyance distance and time of irrigation).Key words: Energy use, pump performance, pumped irrigation, overall seasonal energy, cost (OSEC), Keny

Effect of rain water harvesting and drip irrigation on crop performance in an arid and semi-arid environment

Rainwater harvesting and drip irrigation are possible interventions to enhance crop performance in Arid and Semi-Arid Lands (ASAL). Work was undertaken to evaluate the feasibility of rainwater harvesting for bean production under an ASAL environment in Kaiti Watershed, Makueni District, Kenya. Treatments comprised two rainwater harvesting methods, Zai pits and contour ridges; bucket-kit drip irrigation and a control. No intervention was made to enhance water availability in the crop root zone in the control. The experiment was arranged in a Randomized Complete Block Design with three replicates. Each of the 12 experimental plots was planted with beans (Phaseolus vulgaris L.), variety GLP 2. Soil moisture content and pan evaporation were measured daily for 100 days and runoff after every rainfall event. Crop height was measured once a week and grain and biomass yield were determined at the end of the growing season. Soil moisture content and crop performance were significantly influenced by drip irrigation but not by rainwater harvesting. In drip irrigated plots, grain and biomass yield, were 4 tonnes ha-1 and 9 tonnes ha-1 respectively compared to 3.5 tonnes ha-1 and 7.5 tonnes ha-1 respectively, in the control plots. Drip irrigation effectively maintained adequate soil moisture resulting in better crop performance while rain water harvesting methods failed to significantly enhance soil moisture content and crop performance. This study indicated that rainwater harvesting makes a difference in runoff when the 14 Day Antecedent Precipitation (14DAP) exceeds 80 mm. However, the grain yield obtained in all the plots was higher than the national average of 0.36 tonnes Ha-1. It is recommended that further research be done under different rainfall conditions to confirm the conditions under which the benefits of rainwater harvesting using contour ridges and zai pits can be realized in the enhancement of crop performance in ASAL conditions.Key words: ASAL, soil moisture content, Phaseolus vulgaris L, Zai pits, contour ridges drip irrigation, rainwater harvestin

Application of Ihacres Conceptual Rainfall-Runoff Model to Simulate Daily Stream Flow in Upper Tana Basin, Kenya

Stream-flow measurements are important for water resources assessment and management. In Kenya, inadequate streamflow data poses a major challenge to water resources assessment and management. Application of rainfall-runoff models to the catchments can be used to generate streamflow data. A lumped conceptual rainfall-runoff model IHACRES was applied to six medium sized catchments in the Upper Tana River Basin of Kenya. The model IHACRES was chosen because it requires only catchment area, streamflow data and a surrogate variable representing evaporation such as temperature. In addition, it has only two parameters to be varied during calibration. Streamflow data for the six catchments spanning six years was used in the present study. Simulated streamflow was compared with the observed streamflow for these catchments and the goodness of fit evaluated. The calibration R2 ranged from 0.57 to 0.85 while the simulation R2 ranged from 0.55 to 0.77 for all catchments. The Nash-Sutcliffe (1970) efficiency ranged from 0.78 to 0.91 for calibration and from 0.77 to 0.88 for simulation. Sensitivity tests were also carried out using results for one of the catchments. IHACRES is capable of simulating daily streamflow given concurrent daily rainfall and temperature data and offers a possibility of infilling missing data or generating a long series of streamflow data for water resources management in the Upper Tana River basi

Evidence of groundwater vulnerability to climate variability and economic growth in coastal Kenya

Climate change and future abstraction regimes will influence the availability of groundwater resources. To alleviate any potential negative effects on aquifer systems and dependent industrial and human uses, it is important to develop long-term water management plans. This study evaluates the effect of climate change and future increased groundwater demand from a coastal aquifer located in Kwale County in southern Kenya. A previously calibrated numerical groundwater flow model has been used as an assessment tool to study how future climate (precipitation and temperature variation) and groundwater abstraction changes will affect the aquifer system. The groundwater flow model was built to simulate the period 2010 to 2017, and eight future model scenarios were developed that cover six hypothetical future years. Future groundwater abstraction has been based on current allocations and future estimates made by Kenya’s Water Resources Authority. Future rainfall scenarios have been constructed based on a long historical data series (from 1959 to 2017) and the Standard Precipitation Index. The main results show that future abstraction increases due to economic growth exerts a minimum impact compared with expected climate variability. Recharge depends on intense rain events with important implications for both dry periods and for an average rainfall year. A succession of extended dry seasons may affect all water users. However, the groundwater level decline in the local shallow aquifer can reach five meters, with important consequences for local community water supplies. The most significant groundwater decline in drought periods is observed in the area surrounding the pumping wellfields in the deep aquifers, where the effects of drought and significant abstraction are multiplied. However, the effect of increased abstraction on the shallow aquifer system is limited. Despite groundwater level decline observed during prolonged dry periods, a dry period followed by a humid period leads to the relatively swift recovery of the groundwater system

Supporting multifunctionality through realistic, conditional and voluntary actions to enhance trees as source of environmental services

In this final section we will discuss the interrelationships among people, trees and local climate (the inner circle of the diagram), and all the surrounding issues at national and international levels, and then relate our current understanding and knowledge of these interrelations to opportunities for action. We pick up the thread from Chapter D and return to the issue of multifunctionality of landscapes and the way human drivers and institutions that influence the landscape can themselves be modified. This section describes the public debate and the development of new mechanisms to support multifunctionality of landscapes, in four chapters