Sustainability of water resources development for Malawi with particular emphasis on North and Central Malawi

The world population regardless of location and development stage needs energy and water. According to the United Nations, the present world population stands at about 6.7 billion with an average annual growth rate of 1.3%. Population increase calls for increased allocation of water for domestic use, agriculture and industrial use. The increased water allocation among different sectors has always resulted in conflicts among users, and stress on freshwater environment. Therefore it is essential that water resources be developed in a sustainable manner to accommodate future generations to meet their water needs. In recent years studies regarding stress on water resources due to population increase have always been done without considering the effect of climate change while studies on the effect of climate change on river flows have always ignored the effect of population increase. An assessment of the sustainability of the water resources primarily of the Central and Northern highland river basins of Malawi is presented in this thesis based on basin hydrology, human health, environment and climate change. A complete hydrological data set is not readily available in developing countries like Malawi. That being the case, a method of estimating missing data in hydrological data records has been presented. Climate change predictions have been done based on United Kingdom (UK) Meteorological Office Hadley Centre HadCM3 experiments. All the river basins in the Central and Northern part of Malawi drain into Lake Malawi. Lake Malawi plays a major role in the provision of energy for the country and water supply to the southern part of Malawi through its outlet Shire river. Planning of alternative water resources schemes on river basins in the northern part of Malawi needs an assessment of the hydrological behaviour of the lake. In view of this, the report further explores the sustainability of water levels of Lake Malawi based on generated climate scenarios. A method of extending river flow records based on climate scenario is presented. In the proposed method a simple rainfall runoff model of Linear Perturbation Model has been used to extend flow records with inputs from HadCM3 experiments. The results showed a good correlation between predicted and observed series. Climate change prediction downscaled from HadCM3 general circulation models using statistical techniques were used to create 25 year river flow scenarios from 2001 to 2100. The thesis further reports a method of extending evaporation data based on climate change prediction since evaporation plays a major role in the development of irrigation. The future evaporation scenarios have been incorporated in the water balance model of Lake Malawi for the assessment of sustainability and future water levels of the lake. A method of formulating water resources sustainability index through the integration of knowledge from hydrology, human health and environment is presented. The Water Sustainability Index has been developed as a tool for assessment of multipurpose water resources development comparing one river basin with another in a sustainable manner. In conclusion the method proposed in this thesis can be used as a tool for assessing the strategic sustainability of water resources development as planned under the Malawi National Water Development Programme (MNWDP) phase II. The goal of MNWDP II is to develop a water resources investment strategy for Malawi by looking at the current available water resources and the impact of developing these water resources. Although it is hoped that the methods can be of benefit under MNWDP II, investigations into other techniques would be beneficial.