Komati Downstream Development Project (KDDP)
September 23, 2024
High Value Crop and Horticulture Project (HVCHP)
September 23, 2024Background
The Kingdom of Eswatini experiences high rates of land degradation which result in the loss of land productivity, ecosystem services and incomes to local communities. It is estimated that land degradation costs the country up to US$100 million per annum, which is equivalent to 3% of Eswatini’s Gross Domestic Product (GDP). The Mntjuzalala catchment in the Ngololweni community falls within one of Eswatini’s land degradation “hotspots”. It is found in the Ingwavuma Basin, in the Highveld of Eswatini and is located in the Shiselweni region, at coordinates 31°06’19.05’S and 31°25′25.21’E. The Mntjuzalala catchment, although small, experiences varying land use practices which are impacting soil stability in different ways. The area is mainly sloppy and is characterised by sparse vegetation, shrubs, grassland and bare areas. These characteristics increase vulnerability to soil erosion which will impact on the sediment load downstream and impacting negatively on the proposed dam to be built downhill.
A study of soil erosion and sedimentation in Mntjuzalala catchment area
The Government of Eswatini through the Eswatini Water and Agricultural Development Enterprise (ESWADE) is implementing the IFAD-funded Smallholder Market Led Project (SMLP) in 37 Chiefdoms in the rain-fed Middleveld and Lowveld areas of the Lubombo, Shiselweni and Manzini Regions within the country.
The project aims to assist rural farmers to improve their income through developing irrigated communal command areas and creating access to markets. It invests in rainwater harvesting at the homestead and in fields, in rehabilitation and construction of new small irrigation dams and in erosion control with a view to enhancing the productivity of land and water resources in a sustainable manner. Feasibility studies were conducted to inform the construction of dams.
One such study was conducted in the Mntjuzalala catchment area to determine the rate of soil erosion and sedimentation to estimate the useful lifespan of the proposed small irrigation reservoir that is to be constructed in the area.
This would assist in developing soil loss and sediment yield management measures in the catchment. The study also made use of the Revised Universal Soil Loss Equation (RUSLE) model which included installations of runoff plots and grab sampling on the proposed reservoir site, secondary data in the form of maps, reports publications and geographical information system data were also used.
The study area has an existing smallholder irrigation scheme with approximately twenty seven members who produce and supply vegetables to small businesses as well as larger supermarkets in the country.
A focus group discussion was held with community stakeholders, consisting of traditional leaders, chiefdom development committees and irrigation scheme members to obtain local stakeholder opinion on the prioritization of sustainable land and water management strategies.
Objective
The main objective of the study was to estimate the rate of soil erosion within the Mntjuzalala catchment and determine the impact on sedimentation rate and useful lifespan of the proposed reservoir.
Figure 1: Study area
Table 1: Characteristics of the Proposed Reservoir
|
Parameter |
Characteristics |
|
Catchment area |
611 ha |
|
Storage Capacity |
126,000 m3 |
|
Dam height |
7 m |
|
Length of embankment |
180 m |
|
Drawback |
600 m |
|
Crest Width |
6 m |
|
Spillway width and depth |
16m, 1.5m |
|
Spillway discharge |
41.3 m3/s |
|
Volume of earthworks |
3279480 m3 |
Findings and recommendations
The study observed that since 1988 there has been huge change in land cover and land use in the catchment area. In 1988 forests covered 13.3% of the catchment while grasslands covered 39.9%. Grasslands have been taken over by invasive species such as the sandanezwe, bukhebeletane, indodengaziwa, and many others. An increase in human settlements from 11.5% to 19.7% and the associated increase in human activities has resulted in the loss of wetlands from 32% to 4.5% between 1988 and 2018.
Figure 2: Land Use Changes from 1988-2018 in the Mntjuzalala Catchment
From estimated soil loss, it was observed that annual average sediment yield was 82.04 tonnes/year and sediment delivery ratio (SDR) was 0.46, thus sediment deposit on reservoir site was 30.19 tonnes per year. The sedimentation rate or annual storage loss was estimated at 1.55% per annum, which would lead to 50% of the reservoir storage having been lost after 32 years when the annual sediment deposition would be 1946.75 m3. In terms of sediment sources, it was observed that this earth dam site is adjacent to gullies and cattle tracks which are active sources of sediments during the rainy season.
Figure 3: Gullies Forming in the Steep Slopes Within the Mntjuzalala Catchment
Proposed sustainable land and water management strategies
The following strategies were developed in consultation with community stakeholders.
|
Strategies |
Cost |
Social Acceptance |
Political Will |
|
Soil Conservation and runoff control infrastructure installation
|
High |
High |
High |
|
Community awareness raising on sustainable land and water management
|
Low |
High |
High |
|
Capacity building to ensure sustainability of the water infrastructure |
High |
High |
High |
|
Implementation and monitoring of Chiefdom Development Plan
|
Low |
High |
Medium |
|
Enforcement of existing laws and policies in relation to environment, land and water management
|
Low |
Medium |
Medium |
Proposed actions
- Soil Conservation and runoff control structures
- Soil Conservation and runoff control structures
- Planting of trees/grass along the proposed surrounding of the reservoir.
- Proper maintenance of gravel road and management of storm water.
- Construction of a check dam upstream where there is more erosion.
- Implementation and monitoring of Chiefdom Development Plan
- Training community leaders and traditional authorities on the importance of the chiefdom development plan.
- Assist community to mobilize resources to successfully implement the chiefdom development plan.
- Establish a committee that will be responsible for land and water management in the community.
- Establish community committees to ensure safeguarding of natural resources including land and water.
- Training and mentoring of such committees by government and other agencies.
- Establishment of partnerships with government, non-governmental, private sector and individuals to strengthen community’s actions in sustainable management of water and land.
- Ongoing sensitization of community members on the sustainable management of natural resources.
- Capacity building to ensure sustainability of the water infrastructure.
- Provision on expert personnel to manage the reservoir.
- Development and implementation of operational rules and procedures.
- Establishment of infrastructure operation and maintenance committee.
- Enforcement of existing laws and policies in relation to environment, land and water management.
- Raise awareness about the policies pertaining to sustainable management of environment, land water resources at catchment level.
- Enforce penalties on mismanagement of natural resources which may affect sustainability of the project.
- Development of chiefdom bylaws in relation to the national laws and policies.
Recommendations
- There is a strong need for awareness raising among all stakeholders involved in development, about the importance of sustainable land and water management.
- There is need to undertake yearly soil loss measurements and to collect adequate soil data for validation of modelled soil loss and to inform and adjust catchment management practices and plans.
- The Chiefdom Development Plans should be periodically monitored and reviewed to promote sustainable land and water resources management.
- There is need for policy regulations and enforcement of integrated catchment management in the Mntjuzalala catchment and the country at large to ensure sustainable land and water resources management.
References
Swaziland National Climate Change Policy, 2016.
Nkonya, A. Mirzabae, J. von Braun. Economics of Land Degradation and Improvement - A Global Assessment for Sustainable Development. Springer Open, Heidelberg New York Dordrecht London, 2016.
Hlanze, D.K. (2019). Estimating soil loss rate and sediment yield of the proposed Ngololweni Earth Dam, Kingdom of Eswatini. MSc. Thesis. Master of Integrated Water Resources Management, University of Dar es Salaam.
1 Comment
We are a group of volunteers and starting a new scheme in our community.
Your site provided us with valuable information to work on.
You’ve done an impressive job and our entire community will be thankful to you.