Water harvesting and improved water management for enhancing agricultural productivity in smallholder irrigation schemes in Uganda : case study of Doho irrigation rice scheme

This thesis focuses on devising strategies to enhance agricultural productivity in smallholder irrigation schemes and rural livelihoods. The research questions answered in this thesis are: how can the water management in smallholder irrigation schemes be improved to match water supplies to field water requirements, to enhance equitable water distribution among upstream and downstream farmers and to make effective use of unevenly distributed rainfall; what are the institutional issues affecting water management for food production in Uganda; and what is needed for Uganda to achieve food security? Data for this study has been obtained through iterature review, field measurements and through key informant interviews.lThis study reveals a need to embrace supplementary irrigation for rice cultivation. The frequency of occurrences of critical dry spells of duration greater than 15 days in Doho catchment is 80%. This means that these critical dry spells virtually occur every year. Assessment of soil water plant relations reveals that the effective rainfall in the area is not sufficient to supply the crop water requirement for rice cultivation. The analysis of dry spells demonstrates that the problem of rainfed agriculture in Uganda is not only limited to low productivity but is further aggravated by a high degree of uncertainty due to the erratic nature of rain. The water balance study at scheme level reveals a need for water harvesting in combination with storage to improve on the water distribution. The study shows that with timely planting and better timing of irrigation supplies to meet crop water requirements, there is potential to increase the rice yields from the current levels of 1.9 - 2.8 tons/ha to 6 tons/ha. This represents a 53 to 68 increase in yields.%A decision support model - IDRAMAP - has been developed as planning and operational tool for the main irrigation system. Within each, block responsibility for water allocation and distribution lies in the hands of the Water Users Association. The model is based on the water balance for paddy fields. The irrigation and drainage requirements are determined considering the amount of expected daily average rainfall and reference evapotranspiration, the current field conditions of water depth and the stage of growth of the crop. The model provides a flexible database linked to a weather station in which the user enters the design, the meteorological, and the agronomical information. In case of water shortage, an equal reduction factor is applied to all the blocks. The results of the model are displayed in the form of tables and graphs. The user can visualize at any moment the actual situation or the past performance. The model is useful in data capture and storage and is time saving. Data storage is also crucial in monitoring and evaluation of the irrigation scheme performance, promotion of equitable water distribution and for accountability to the water users who have to pay for the irrigation service. User training in field data collection and setting of discharges at control structures is paramount. Training is also essential to sensitize all stakeholders on the need for accurate and timely field procedures.This thesis shows that agricultural development and transformation in Uganda requires decisive efforts on five pillars: water; markets; land; science and technology; and health. Institutional provisions necessary in promoting irrigation development are assessed in this thesis including but not limited to streamlining the land tenure system, cost sharing and cost recovery, policy and legal issues, gender related issues and water rights