services - water resource studies

Water resource management is the activity of planning, developing, allocating and managing the optimum use of water resources. Water resource planning studies for short, medium to long term or water allocation plan, encompass a number of activities or assessments.

 

These assessments include:

  • Determine available water in the catchment from observed information or using hydrological models (preferably using fully physical based models).

  • Determine water use in the catchment from observed information ( e.g. water meters, satellite information) or using hydrological models.

  • Assess water availability of catchments or determine water yield of the system.

  • Develop operating rules based the country institutional arrangement for optimum and equitable water use to advance social and economic progress.

The assessment of water availability involves historical and stochastic determination of reservoirs and systems yield as well as the risk of water scarcity in future due to climate variability and climate change. Ekosource has been involved in a number of water resource studies, and two of the projects are discussed on this page.

Project #1

Progressive Realisation of the IncoMaputo Agreement (PRIMA): System Operating Rules for the Incomati and Maputo Watercourses.

Description of the Project:

The project aimed at developing a set of operating rules for the Incomati and Maputo watercourses. As part of this project there was a requirement to develop a set of integrated operating objectives which could be used to develop the operating rules to manage the entire catchment area.   Setting integrated operating objectives for the entire Inco-Maputo area was a challenging task. Complexity involved with the task revolved around the arrangement that these large basins are split between 3 countries, which each have a number of different management units and institutional structures to address operational water management challenges. The key challenge was to optimise the local resource usage while at the same time not compromising the system as a whole. A multi-tiered approach to the management of the basin was implemented, where overall key management objectives were produced at a global level and the systems were operated on a local basis while ensuring compliance with the larger overall objectives.

Description of Actual Services:

In terms of the process that will be followed in this particular component of the project which focuses on the development of the operating rules, a four step approach was undertaken:

  • The operating objectives were defined.

  • An operating rule was determined for the key resources (this was be done through interviews and where no operating rules were present, the consultants developed their own operating rules).

  • The operating rules were tested to ensure there was compliance with the overall operating rules and objectives of the entire catchment.

Finally compliance was tested on both a longer and shorter term basis through regular system updates.

Project #2

Water availability for Lunsemfwa catchment, Zambia.

Description of the Project:

The Lunsemfwa River is a major tributary of the Luangwa River, forming part of the Zambezi River basin. The major users of the water resource, provided by the river, are: large scale commercial agriculture and the Lunsemfwa Hydro Power Company’s (LHPC) Lunsemfwa Power Station. Lunsemfwa and Mulungushi Dams' Power Stations were sold under the privatization programme in 1991. The sale and purchase agreement was expected to include the transfer of water rights WDB/40 and WDB/40a as a pre-requisite to the sale. LHPC applied to the Water Board for Water Rights as held by ZCCM.

The Lunsemfwa catchment has predominantly irrigation users (approx. 15 % of total water right) at the upper part of the catchment, and a large hydropower user at the outlet (approx. 85 % of water right) of the catchment. The water resource yield assessment that was performed in this project was to determine the water availability in the catchment and the potential impacts on system yield if the proposed Chimsoro farm expansion was to be implemented. This included the possible development of the proposed Lunsemfwa Dam Project. The water resource yield assessment of a catchment consists of a hydrological assessment using an observed stream flow or rainfall-runoff modelling, and a yield assessment using a water resources network modelling framework. In this project, the rainfall-runoff modelling was performed using the one point rainfall data collected from previous studies and the water use information that was extracted from satellite coverage from the period of 1998 to 2014.

 

Furthermore, the rainfall data was adjusted to take into account spatial variability using the MAP (mean annual precipitation) information.

Description of Actual Services:

The requirement of the project was to assess the water availability of the catchment and assess a number of development scenarios to determine the feasibility of the developments. The scenarios and development objectives that were assessed include:

Scenario 1:

  • Assess the sustainability of the 2750 hectares of wheat/soya Chimsoro farms at risk of failure level of 1:10 years return period, which is the run of river capacity at Chimsoro BAU (business as usual), excluding LHP demand;

  • Recommend the size of an off channel storage that is required for the 2750 hectares of wheat/soya at Chimsoro farms to be viable at 1:10 years risk level ;

Scenario 2:

  • Assess the sustainability of 5500 hectares of sugar cane at Chimsoro farms, drawing water from run of river without an off channel storage, excluding LHP flow demand;

  • Recommend size of an off channel storage that is required for the 5500 hectares of sugar cane to be viable at 1:10 years risk level;

Scenario 3:

  • To assess sustainability of 5500 hectares of sugar cane at Chimsoro farms and 4100 hectares of sugar cane for out-growers and 1900 hectares new development, excluding LHP flow demand at 1:10 years risk level;

Resource development objectives:

  • A matrix of storage requirement was developed for the 90% assurance of supply or 1:10 years risk level. The matrix was to include the following scenarios:

  • Mix of conversion – 60% conversion from current cropping mixing to sugar cane and 40% of development of new sugar cane lands. This was captured in Scenario 2 analysis of this study. Where 4100 hectares of wheat/soya and 5500 % hectares of sugar cane is considered.

  • Best Case - 100 % conversion from current cropping to sugar cane. This objective was analyzed as part of Scenario 3 of this study, where all the wheat/soya in the Lunsemfwa catchment wass converted to sugar cane and new development was also included in the scenario.

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Images for Project #2

Figure 1: Location of Lunsemfwa Catchment

Figure 2: Moving average for mean annual precipitation from the Martheodina Rainfall Station

Figure 3: Moving average for simulated streamflow at Chimsoro pump station

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