Addressing impact of Bagree dam spillage in White Volta River basin in Ghana [Article]

This year’s opening of the spill gates and release of water from the Bagre Dam is the earliest since 2007 (the spill gates were opened on August 10, 2020 which is three weeks early than the earliest date previously recorded).  So far, the daily average rate of release from the Bagre Dam has been quite high between 76.5 m³/sec and 473.1 m³/sec with an exceptional rate of 1,108.02 m³/sec released on 27 August 2020. It is also significant to note that the peak rainfall in the White Volta Basin and Burkina Faso is expected to occur in the middle of September to early October.

To date, several farmlands with the upstream sections of the White Volta (especially Bawku Municipal, Bawku West, Talensi and Nabdam Districts) have been flooded. Should the situation prevail in September and November 2020, it is anticipated that the flooding will affect lives and settlements as well as human health through pollution of potable water sources such as boreholes/wells. Additionally, the financial costs of relief and emergency responses including recovery of property and livelihoods are estimated to be colossal.

Accordingly, government is committed to build on its earlier initiative and eager to take urgent measures to tackle the current unexpected flooding within the White Volta Basin.

Government Earlier Initiative

In early 2019, the government tasked a Ministerial committee consisting of the Ministers for Food and Agriculture; Works and Housing; Sanitation and Water Resources; and Environment, Science, Technology and Innovation to develop and implement a short-term plan to mitigate the impact of the perennial flooding in the White Volta Basin exacerbated by the spillage of the Bagre Dam.

The Committee worked through technical experts assembled from the Water Resources Commission, Hydrological Services Department, the Ghana Irrigation Development Authority, and Water Research Institute of the Council for Scientific and Industrial Research. The 48 Field Engineers Regiment of the Ghana Armed Forces was also engaged in the assignment.

The short-term plan was considered as an emergency, mindful that:

• the major Pwalugu multi-purpose dam to serve as flood control measure amongst others, is to be constructed within the next four years; and
• a single intervention is not sufficient to produce the needed results and, therefore a combination of both structural and non-structural measures is desired.

The plan that had targeted, internal and localized structural interventions with relatively little investment, was to:

• dredge the confluences of the four major tributaries of the White Volta (Sissili, Kulpawn, Nasia and Nabogo) and the main White Volta River, and
• introduce and provide farmers with early maturing crops to enable cropping and harvesting produce before the annual flooding.

Execution of Short-Term Interventions

All the interventions started with consultations with the relevant District Assemblies and engagements with the affected communities (132 in number), their chiefs, and opinion leaders.

The dredging intervention was carried out in two phases. Phase 1 involved the use of excavators and bulldozers mainly on the Nasia and Sissili rivers, which are the most heavily silted. Work was also carried out on the Nabogo River.  Phase 2 followed with the use of 4 dredgers on the Nasia and the Sissili rivers in view of the high water levels and the flood period.

The assignment was successfully executed from May to December 2019. At the end, a cumulative length of about 39 kilometres and 548,720 cubic meters (27,436 of 20-tonnes truck loads) of sand and silt materials (estimated value of Ghana cedis 2.7 million) had been dredged. The dredging allowed for the free flow of the rivers and increased their capacities to hold more water, which otherwise would have ended as flood waters causing destruction to live and property.

In order to maximise the benefits of the dredging works, the compost-grade material dredged from the Nasia River was given to farmers for use on farmlands to improve soil fertility and filling of death-trap trenches in Nasia community. On the other hand, the high grade sand material dredged from the Sissili River, which is suitable for construction of buildings, drains and bridges among others, has been made available to the Mamprugu Moanduri and Builsa South districts to be put to good use for the benefit of the communities in the project areas.

In the case of introducing and providing farmers with early maturing crops to enable cropping and harvesting produce before the annual flooding, the distribution of maize started in early May 2019 with the sensitisation of farmers, validation of acreages of farmlands and seed requirement. The intervention ensured that:

• 139 communities in 11 districts and 11, 222 farmers (7,553 males and 2,999 females) benefited.
• 14,361 hectares of farmlands and 6,702 bags (301.6 metric tonnes) of improved maize seeds were distributed and planted by the farmers.
• A total of some 43,084 metric tonnes of maize was harvested by the middle of September 2019.

Evidently, the short-term interventions executed at a total cost of Ghana Cedis 22.6 million served the intended propose of assisting to reduce the causes of the floods and the attendant damages.  Indeed, at the end of the rainy season in November 2019 there were no reports of extensive flooding of the dredged areas potentially prone to flooding in the past. The destruction of crops and farmlands also reduced significantly in the area.

Planned Interventions for Current Situation

The results of the initial interventions carried out in 2019 show that dredging of the White Volta River and its tributaries should be a periodic maintenance activity. Furthermore, greater positive impact can be made should other critical areas within the basin be also tackled.

Two field reconnaissance surveys carried out in May and early July 2020 confirm that extensive upstream sections of the White Volta River are shallow due to siltation. In some areas the river depth is as shallow as 0.2 metres, while other sections of the river have sediment levels above the water surface, creating islands with heavy vegetation.

These areas have been mapped for the following urgent interventions:

• Engaging 42 communities within the Bawku West (25); Nabdam (5); and Talensi (12) districts in the Upper East Region.
• Dredging the main White Volta in the upstream areas of Yarugu (Bawku); Pwalugu; and confluence of Sissili/Kulpawn.

In view of the prevailing high flows in the main White Volta, dredgers will be used throughout the dredging exercise. It is expected to cover a cumulative dredged area of about 30km within the upstream section from the border with Burkina Faso; upstream and downstream of the Pwalugu bridge including the proposed Pwalugu dam site; and upstream the confluence of the Sissili/Kulpawn.

The estimated budget for the entire exercise is Ghana Cedis 29.6 million, including the dredging works, community engagement, restoration/stabilization of dredged river banks, documentary production, and operations.

Expected Impacts/Effects

The urgent exercise is expected to produce threefold benefits:

• minimize the impacts of flooding upstream of the main White Volta within the Yarugu (Bawku) area, around the Pwalugu area, and the confluence of the tributaries;
• improve flows into the Pwalugu dam, and facilitate flow from the Sissili and Kulpawn tributaries; and
• minimize or reduce sedimentation of the Pwalugu reservoir.

The anticipated dredging of the upstream sections of the White Volta will not to be carried out exclusively.  It will be done mutually and complement the ongoing non-structural measures, notably the provision of forecast and early warning information, exchange of data and information on the spills, consultations with managers of the Bagre dam, community education, awareness creation, and emergency response/operations.