Quantifying green water flows for improved Integrated Land and Water Resource Management under the National Water Act of South Africa: A review on hydrological research in South Africa (original) (raw)
Related papers
South African research in the hydrological sciences: 1999-2002
2000
The principal activities of South African researchers in hydrology and water resources during the reporting period have been con- cerned with ground- and surface-water interactions, rainfall-runoff modelling, the establishment of improved regional water resource databases, the management of transboundary water resource systems, the ecological reserve, and quantifying the impacts of streamflow reduction activities. Most of these studies have focused on
2014
Quantification of the water cycle components is key to managing water resources. Remote sensing techniques and products have recently been developed for the estimation of water balance variables. The objective of this study was to test the reliability of LandSAF (Land Surface Analyses Satellite Applications Facility) evapotranspiration (ET) and SPOT-Vegetation Normalised Difference Water Index (NDWI) by comparison with ground-based measurements. Evapotranspiration (both daily and 30 min) was successfully estimated with LandSAF products in a flat area dominated by fynbos vegetation (Riverlands, Western Cape) that was representative of the satellite image pixel at 3 km resolution. Correlation coefficients were 0.85 and 0.91 and linear regressions produced R2 of 0.72 and 0.75 for 30 min and daily ET, respectively. Ground-measurements of soil water content taken with capacitance sensors at 3 depths were related to NDWI obtained from 10-daily maximum value composites of SPOT-Vegetation i...
Hydrology and Earth System Sciences, 2014
Integrated water resources management is a combination of managing blue and green water resources. Often the main focus is on the blue water resources, as information on spatially distributed evaporative water use is not as readily available as the link to river flows. Physically based, spatially distributed models are often used to generate this kind of information. These models require enormous amounts of data, which can result in equifinality, making them less suitable for scenario analyses. Furthermore, hydrological models often focus on natural processes and fail to account for anthropogenic influences. This study presents a spatially distributed hydrological model that has been developed for a heterogeneous, highly utilized and data-scarce river basin in eastern Africa. Using an innovative approach, remote-sensingderived evapotranspiration and soil moisture variables for 3 years were incorporated as input data into the Spatial Tools for River basin Environmental Analysis and Management (STREAM) model. To cater for the extensive irrigation water application, an additional blue water component (Q b ) was incorporated in the STREAM model to quantify irrigation water use. To enhance model parameter identification and calibration, three hydrological landscapes (wetlands, hillslope and snowmelt) were identified using field data. The model was calibrated against discharge data from five gauging stations and showed good performance, especially in the simulation of low flows, where the Nash-Sutcliffe Efficiency of the natural logarithm (E ns_ln ) of discharge were greater than 0.6 in both calibration and validation periods. At the outlet, the E ns_ln coefficient was even higher (0.90). During low flows, Q b consumed nearly 50 % of the river flow in the basin. The Q b model result for irrigation was comparable to the field-based net irrigation estimates, with less than 20 % difference. These results show the great potential of developing spatially distributed models that can account for supplementary water use. Such information is important for water resources planning and management in heavily utilized catchment areas. Model flexibility offers the opportunity for continuous model improvement when more data become available.
Hydrometeorological Research in South Africa: A Review
Water, 2015
Water resources, particularly in arid and semi-arid regions of the world are of great concern, as they are closely linked to the wellbeing of humankind. Sophisticated hydrological prediction tools are required to assess climatic and hydrometeorological conditions, as they impact the sustainability of water resources as well as water availability. Research and data collection activities from multi-hydrometeorological sensors (e.g., gauges, radars, satellites) form the basis for quantifying the impact of extreme episodes along the hydrologic phases that manifest in terms of the magnitude, duration and frequency of floods, droughts and other hydrometeorological hazards that affect water resources management. A number of hydrometeorological research activities have been reported in the literature by various researchers and research groups globally. This contribution presents (a) a review of the hydrometeorology resource landscape in South Africa; (b) an analysis of the hydrometeorology services and products in South Africa; (c) a review of the hydrometeorological research that has been conducted in South Africa for the last four decades; and (d) highlights on some of the challenges facing the sustained advancement of research in hydrometeorology in South Africa.
Geoscience Letters, 2021
An assessment study on the impact of land use change through afforestation on catchment water balance was carried out in one of the semi-arid quaternary catchments (C52A) of the Modder River Basin located in the central region of South Africa. The study used ArcGIS and the Soil and Water Assessment Tool (SWAT) to create scenarios of forest cover areas and to simulate the water balance of C52A, respectively. Climatic data from 1993 to 2020 were used to simulate the catchment water balance. The climatic data from 2011 to 2020 were generated using SWAT weather generator while the rest was obtained from South Africa Weather Service at three weather stations located within C52A catchment. In the C52A quaternary catchment it was envisaged to increase forest cover by considering afforestation on pastureland that is found on slopes > 8% and > 3% which created two forest scenarios. The baseline land use [Land use 2000 (LU2000)] which is taken as the base scenario in this study has abou...
Water SA, 2004
Rapid assessments of water resource availability in South Africa have been facilitated by the availability for a number of years of a national data set of naturalised monthly flow time series. However, these data are only available for moderate to large catchments (referred to as quaternary catchments). In the absence of further information it has often been the practice to apply a simple catchment area-based scaling factor to estimate subquaternary scale flow characteristics. This has proved to be problematic in many studies. The paper presents a comparison of quaternary and subquaternary flow data using 41 gauged catchments and develops a simple approach to scaling based on estimates of the mean annual rainfall characteristics for the two areas. The use of the scaling method in a model designed to provide preliminary, low-confidence, estimates of environmental flow requirements suggests that it represents an improvement. However, there is still a need for a method that allows flows of different magnitudes and frequencies of exceedance to be scaled differentially.
In this study, GIS and remote sensing tools were combined with hydrological modelling to identify the impact of afforestation on basin hydrology in the Tsitsa basin, South Africa. Initially, hydrological characteristics such as long-term rainfall and temperature pattern as well as basin runoff dynamics were delineated analyzing available hydro-meteorological time series. Additionally, double mass plots of the runoff of the Tsitsa and its tributary Mooi were analysed in order to evaluate runoff dynamics with regard to spatio-temporal rainfall pattern. These efforts revealed a significant reduction of the Tsitsa runoff beginning in the 6th year after the first plantations. Furthermore, water balance was simulated using the process oriented, hydrological model JAMS/J2000 [1] to quantify the impact of these land use changes on runoff dynamics. Addressing the distributive concept of the J2000 model, the Tsitsa catchment has been divided into Hydrological Response Units (HRUs). Since a thorough hydrological system analysis has shown that slope, soil type, land use, geology and aspect are the hydrologically most relevant components, these input layers were used for a GIS-based overlay analysis to provide spatial model entities for the modelling. The model was parameterized using field data and literature values. Thus, it shows that GIS and remote sensing techniques provide proper methods and data for environmental modelling, particularly in large scale applications.
2006
The Comprehensive Assessment (www.iwmi.cgiar.org/assessment) is organized through the CGIAR's Systemwide Initiative on Water Management (SWIM), which is convened by the International Water Management Institute. The Assessment is carried out with inputs from over 100 national and international development and research organizations-including CGIAR Centers and FAO. Financial support for the Assessment comes from a range of donors, including core support from the Governments of the Netherlands, Switzerland and the World Bank in support of Systemwide Programs. Project-specific support comes from the Governments of Austria, Japan, Sweden (through the Swedish Water House) and Taiwan; Challenge Program on Water and Food (CPWF); CGIAR Gender and Diversity Program; EU support to the ISIIMM Project; FAO; the OPEC Fund and the Rockefeller Foundation; and Oxfam Novib. Cosponsors of the Assessment are the: Consultative Group on International Agricultural Research (CGIAR), Convention on Biological Diversity (CBD), Food and Agriculture Organization (FAO) and the Ramsar Convention. Funding support for this specific project was received from the governments of Switzerland and the Netherlands.