Final results and hectare equivalents of ecosystem functionality related to wetland nitrate removal in the upper Goukou River Quaternary catchment. Error. Prioritizing wetlands in the Goukou catchment based on current effectiveness of water quality improvement .. Err.
Introduction
Problem Statement (Motivation)
Therefore, maintenance of water quality and quantity is of great importance to meet the requirements of the Reserve. Despite this, the widely used tool currently assessing wetland health in South Africa (Macfarlaneet al., 2008) does not have a water quality component.
Research Aim and Objectives
Structure of the Dissertation
Chapter Three focuses on the description of the case study site, while Chapter Four describes the materials and methods used to achieve the aims and objectives of the study. Note: the word 'effect' has been used in place of the word 'impact' as much as possible, even though the standard terminology is 'cumulative impacts'.
Wetlands: An Overview
- Definition
- Hydrology
- Hydromorphic Soils
- Vegetation
- Hydrogeomorphic Settings of Wetlands
- Ecosystem Services
- Linking Hydrogeomorphic Type to Hydrological Benefits
- Wetland Rehabilitation Techniques
- Wetlands in South Africa
Finally, depression wetlands occur as a result of the groundwater table intercepting the land (Macfarlane et al., 2008). Preliminary rating of the hydrological benefits likely to be provided by a wetland given its hydrogeomorphic type (Kotzeet al., 2007).
An Overview of WET-Health and WET-Ecoservices
WET-Health
As previously mentioned, the underlying concept of WET-Health is the fact that wetland health is inversely related to assessed impacts (Macfarlane et al., 2008). The overall magnitude of the obtained results is the result of the assessment of the intensity and extent of the impact under assessment and the health of the wetlands is evaluated on a scale from 0 to 10.
WET-Ecoservices
This implies that a low habitat impact score (or deviation from the natural reference state) reflects a high habitat health score (or similarity to the natural reference state). Conversely, a high habitat impact score obtained by an extensively degraded wetland reflects a low habitat health score, i.e.
A Method for Assessing the Cumulative Impacts on Wetland Functions
- Introduction
- Land-cover Change Impact Metric
- Loss of Function Metric
- The Calculation of Functional Effectiveness Scores
- The Calculation of Functional Hectare Equivalents
- Ellery et al.’s (in review) Tool in Relation to Cumulative Impacts
Equations describing the relationship between impacts resulting from reduced wetland surface roughness and the provision of a range of ecosystem services (Ellery et al., in review). Ellery et al. (in review) illustrate this point by referring to a figure of a catchment containing four wetlands (Figure 3).
The Effect of Catchment Land-cover on Water Quality
- A Review of Water Quality
- South African Land-cover
- The Effect of Catchment Land-cover on Water Quality
- Natural Land-cover
- Forest Plantations
- Cultivated, irrigated Land
- Cultivated, dryland Land
- Dongas and Sheet Erosion
- Degraded Vegetation
- Urban residential- high density Land-use
- Residential- rural Land-use
- Urban Commercial Land-use
- Urban Industrial/Transport Land-use
- Mines and Quarries
- Urban Informal Land-use
- Pollutant Loadings from Catchment Land-cover
The National Land Cover Project (NLC) was initiated by the South African Directorate of Surveys and Mapping to map land cover across South Africa, culminating in a standard 31-class land cover classification scheme , presented in Table 133 (DEAT, 2008). The heaviest contributors to TSS and TDS were the urban informal and urban industrial/transport land cover classes, as well as mining and quarrying.
Landscape-level Impacts and Cumulative Effects
Introduction
Davies and Day (1998) go on to justify this claim by introducing what they describe as the "basic units of the landscape" (p.45): catchments. Individual wetlands A single area defined by the boundaries of the wetland itself.
Addressing Cumulative Effects on Wetlands
- Catchment and wetland land-cover and its relation to wetland
However, it should be noted that not all ecosystem services provided by a given wetland can be altered by a change in wetland context, and that the provision of ecosystem services can change to different degrees or in different directions (Kotze , 1999). . An example provided by Kotze (1999) is that while the ability of a wetland to support biodiversity may be compromised due to increased human activity in that wetland's catchment, such as irrigated agriculture, the same implementation of irrigated agriculture can increase the value of wetlands. to ensure the improvement of water quality.
Past Approaches to Cumulative Effects Assessment
While past approaches to assessing cumulative effects are valuable in building an understanding of cumulative effects, the relationship between changes in the provision of ecosystem services to changes in wetland health and their effect on the overall watershed is not addressed, particularly in a South African context. , nor the effects of surrounding land cover types. Moreover, a method to incorporate the consideration of the location of wetlands in the landscape taking into account all these aspects is also not included in these studies.
An Overview of the Analytical Hierarchical Process (AHP)
Additionally, the process allows for values and influences to be accurately incorporated, as well as the incorporation of judgments that are based on intuition and emotion. Finally, such a formalized approach allows for revisions that are gradual and thorough, as well as the task of combining the judgments of different people who have different opinions on the same topic.
GIS Applications to Wetland Research
This has allowed continued exploration into larger, more challenging projects, including assessment of the spatial and temporal characteristics of water resources; as well as scenario evaluation, described by Lyon and McCarthy (1995) as one of the most important contributions of GIS to data analysis. These scenario modeling exercises allow the sensitivity of the variables to the model outputs to be analyzed (Lyon and McCarthy, 1995).
Introduction
The Goukou region was selected as a case study area due to the availability of good data on wetland locations, wetland health status, and surrounding land cover status. The number of wetlands present, the type of land cover types present, and the availability of relevant spatial data and other useful information represented an ideal case study.
Climate
Satellite image indicating the town of Riversdale, the point of convergence of the Vet (from the northwest) and Goukou (from the northeast) rivers and surrounding land cover (Maplandia, 2005). Temperatures in the Riversdale area reach their lowest in July, when the average daily maximum temperature reaches 18.1°C.
Geology and Soils
Greyish sandy, excessively drained soils occur in the southern parts of the study area, while highly structured soils with a marked accumulation of clay dominate in the northern regions. The geology and climate of this area have allowed the creation of many wetlands, especially in the upper reaches of the basin.
Vegetation
From the Langeberg Mountains of this Cape Fold belt, the Goukou River cuts its way through more than 10 km of erosional Cretaceous sedimentary rocks of the Enon Formation, and then the remaining 40 km of the landscape consists mainly of Paleozoic Bokkeveld Shales (Carter and Brownlie, 1990). ). According to DEAT (2000), the Goukou region is dominated by soils with minimal development, usually shallow on hard or weathered bedrock, with occurrence of lime.
Land-cover and land-use
Introduction
The Analytical Hierarchical Process (AHP)
Review of Land-cover Data and Water Quality Criteria
Application of AHP
This form enabled the ranking of land cover classes according to the severity of their effects on water quality. The scores of the land cover classes in between were determined relative to the highest and lowest scoring classes.
The Application of Catchment Scale Analysis
Calculating the Magnitude of Impacts of Land-cover Change on Water
The range of impact scores is then calculated as the impact intensity score (from Table 4) multiplied by the proportion of watershed and wetland occupied by each land cover class (Table 17). Impact intensity ratings for impacts occurring in the upstream catchment of the wetland and within the wetland are rated on a scale of 0 (no impact) to 10 (critical impact).
Calculating the Magnitude of Impacts of Land-cover Change on
- Catchment Impacts
- Onsite Impacts
- Catchment and Onsite Impacts
- Calculating Functional Hectare Equivalents
- Determining Water Quality Enhancement Functionality
Thus, wetland FID 0 was found to have a functionality score of 3.39 for nitrate removal based on a reduction in surface roughness. Applying this methodology, the functional efficiency scores of impacts originating in the wetland (local impacts) for the other ecosystem services evaluated - phosphate capture and toxin removal - were calculated to equal 3.39 and 3.39 for Wetland FID 0.
Calculating the Magnitude of Impacts of Land-cover Change on Water
The series of steps leading to the calculation of hectare equivalents of water quality impairment for individual wetlands. By multiplying each of these sores by the area of that land cover class, hectare equivalents of water quality impairment are determined.
Calculating Overall Effectiveness of Water Quality Enhancement
The final hectare equivalents are therefore equal to ha, which equates to 7.15 hectare equivalents of water quality improvement. Alternatively, hectare equivalents of water quality impairment are calculated by first multiplying the extent of the watershed cover class (10/10) by the impact ratio assigned to that land cover class, which for mining is 1 (Table 25).
Integrating the Spatial Configurations of Wetlands in a Landscape in
The black numbers in parentheses indicate the overall water quality improvement effectiveness score for each wetland, while the number in red indicates the level of wetland inflow (primary, secondary, etc.). East of the catchment, the overall water quality improvement effectiveness score for wetland D is positive, suggesting that.
Prioritisation of Wetlands
- Prioritisation based on Land-cover
- Prioritisation based on Effectiveness of Water Quality Enhancement
- Prioritisation based on Wetland Degradation and Onsite Rehabilitation103
- Scenario One: Prioritisation based on Land-cover
- Scenario Three: Prioritisation based on Wetland Degradation and
- Summary of Scenario Results
The process of determining overall water quality enhancement effectiveness of the basin was reapplied to the changed land cover classes. Wetlands with the five most negative overall water quality improvement effectiveness scores were then targeted for land cover rehabilitation (Table 50).
Rehabilitation of Wetlands of the Goukou Catchment
Introduction
The Analytical Hierarchical Process (AHP)
Review of Land-cover Data and Water Quality Criteria
Gullies and channels, and permanent or seasonal areas of very low vegetation cover compared to surrounding natural vegetation cover, induced by gradual removal of soil and soft rock due to concentrated runoff. 6 Degraded vegetation Permanent or seasonal man-made areas with very low vegetation cover compared to the surrounding natural vegetation cover.
Application of AHP
Scaled scores were then converted to impact ratios, each of which is indicative of the intensity of the impact of that land cover class on water quality. The idea was to determine pollutant loads in the watershed, which would serve as a reflection of the influence of surrounding land cover classes on water quality.
The Application of Catchment Scale Analysis
- Calculating the Magnitude of Impacts of Land-cover Change on Water
- Calculating the Magnitude of Impacts of Land-cover Change on
- Catchment Impacts
- Onsite Impacts
- Catchment and Onsite Impacts
- Calculating Functional Hectare Equivalents
- Determining Water Quality Enhancement Functionality
- Calculating the Magnitude of Impacts of Land-cover Change on Water
- Calculating Overall Effectiveness of Water Quality Enhancement
- Integrating the Spatial Configurations of Wetlands in a Landscape in
The application of the tool developed by Ellery et al. in review) made it possible to determine the functional effectiveness of the wetlands in the Goukou landscape, expressed in hectare equivalents of water quality improvement. By doing this, an idea of the water quality improvement functionality of the catchment as a whole can be obtained.
Rehabilitation of Wetlands of the Goukou Catchment
Prior to rehabilitation, the total efficiency of the Goukou catchment was found to be - 6802.91 hectare equivalents of water quality improvement efficiency as determined in Section 5.3. As was pointed out prior to rehabilitation, it should be noted that only the valley wetlands were focused on in this study and that additional water quality improvement would also have been provided by the hillslope seepage wetlands present and in the stream sections connecting the wetlands.
Benefits and Limitations of the Methodology
Such an improvement in water quality would undoubtedly also be achieved by other types of wetlands not investigated in this study or by Ellery et al. This study only considered valley bottom wetlands, and further improvement in water quality could also have been achieved by the slope seepage areas present in the Goukou River Basin.
Summary
Evaluation of the impact of agricultural practices on the quality of groundwater resources in South Africa, Report to the Water Research Commission, South Africa. The effect of polluted stormwater runoff from Alexandra Township on the water quality of the Jukskei River, MSc thesis, University of the Witwatersrand, Johannesburg.
