Minimum flow – an unresolved issue

As discussed in previous GET FiT Annual Reports, there have been major improvements in the regulatory frameworks and investment climate for renewable energy in Uganda in the past. There are, however, issues where further work is required to establish clear expectations on developers and clear frameworks for decision-making that balance various societal interests in a predictable and transparent manner. Assessing and determining minimum flow(1) requirements for hydropower projects is one such issue.
Fourteen (14) out of seventen (17) projects approved under GET FiT are hydropower projects. By design, these projects result in a major reduction of the natural river flow between the intake and the power house. In the GET FiT projects, this river section is typically 3-4 km long. The release of a minimum flow is a normal mitigation measure to reduce impacts on people and ecosystems along the affected river section. The volume of the minimum flow also directly impacts on the economic viability of a hydropower project, as water that could otherwise be used for power generation remains in the natural river channel. Minimum flows have therefore been a challenging issue in all hydropower projects supported by GET FiT, with developers struggling to derive at a clearly justified minimum flow level and develop appropriate designs to release and monitor it. The inadequate guidance from government agencies and lack of clarity on which methodologies should be applied to arrive at minimum flow releases have complicated the assessment of minimum flows for developers.  This may have resulted in the inefficient allocation of water among competing societal interests (power production, ecosystems, other human water uses) and unequal requirements on developers.
A simple comparison between the GET FiT supported projects can be made my calculating the minimum flow requirement defined by the Government as a proportion of the mean annual flow of the affected river. Figure 7 below shows that there was substantial variation between projects in terms of the minimum flow requirement as a proportion of the mean annual flow. Expanding the sample of projects to non-GET FiT supported hydropower projects in Uganda increases the variation further. The minimum flow requirements would normally include consideration of issues such as loss of power production, human water use interests along the affected river section (domestic water use, water supply schemes, irrigation, etc.), fish and other ecological concerns as well as whether any tributaries downstream of the hydropower intake contribute water to the affected river section, or the presence of alternative water sources. It is therefore important that minimum flow requirements are identified on a project-specific basis, so that the characteristics of the project setting are accommodated for.  As a result, the minimum flow requirements will vary between projects.
Looking at the variation in minimum flow requirements within the GET FiT portfolio and the characteristics of the affected river sections, it is difficult to see any clear correlation between the level of the minimum flow requirement and the water use interests along the affected river sections. For all parties involved, it would be beneficial is there is greater clarity on the methodologies to be applied in assessing the level of minimum flow, including data requirements, assessment methods and procedures to be followed, including key stakeholders to be consulted. Without greater clarity on the above issues, developers will continue to struggle to derive sound minimum flows on a consistent basis. Furthermore, the allocation of water between competing water uses (power production, local water users, ecosystems) may not be the result of a predictable and fair process, where hydropower developers and other stakeholders can engage in an efficient manner to support balanced decisions.


Figure 7  Minimum flow requirements for GET FiT supported projects defined by Ugandan authorities. The minimum flow requirements are shown as a proportion of the estimated mean annual flow. 



(1)  We refer to ‘minimum flow’ rather than the often-used concept of ‘environmental flow’ as the minimum flow requirements defined in Uganda (by the Directorate of Water Resources Management) usually do not have the characteristics of a true environmental flow, namely a description of the quantity, timing and quality of water flows required to sustain freshwater ecosystems and human livelihoods that depend on these ecosystems.