DRIFT incorporating an eco-social system network and time series approach into environmental flow assessments

DRIFT (Downstream Response to Imposed Flow Transformation) is an interactive, ecological-social process and software package to assist with environmental flow assessments and river management decision-making. It was originally developed in the 1990s and has subsequently evolved and been applied in over 50 studies in Africa, South America, Asia and Europe. Early versions provided predicted ecological responses over time to specific flow changes, while the latest version provides responses to flow and non-flow drivers as seasonal time series. Here, an ecosystem or eco-social network is built for the river, with links between driver and responder indicators, and relationships created for each link. The network and relationships are developed and entered into the software by specialists based on available data and their knowledge. A range of scenarios is explored through the predicted indicator time series, discipline and site level ecological integrity, and social well-being. While DRIFT models vary in complexity, they are all based on relatively simple fundamental principles and arithmetic. Sequential averaging and summation through the system network is used to calculate an indicator’s response to different drivers for successive seasons over time, while the discipline and site level summaries are found using weighted summation of indicator results and individual discipline results, respectively. Information from different specialist areas is therefore processed in the same way, thereby enabling coherent integration across disciplines

Experimental and numerical analysis of river lake system and non-traditional water usage in a new Eco-City

In recent years, Eco-City, which is designed with consideration for environmental impact and is inhabited by people dedicated to minimisation of required inputs of energy, air pollution and water pollution, has emerged as a way to address sustainability issues by adapting it to their local needs and context. The sustainability of urban water resources, water recycling and more efficient use of water resources will be the key features of the Eco-City. The current study takes Sino-Singapore Tianjin Eco-City as an example to investigate the sustainable use of water resources which focus on non-traditional water usage and ecological water requirements assessment. Firstly, the potential non-traditional water supply was evaluated based on the data acquired from the gauging station and the Eco-City planning data. It was found that rainwater has a great potential for domestic use in the Eco-City from June to September. Differing from other water consumption, ecological demand of the river lake system in the Eco-City was analysed by minimum ecological water requirements determination. An improved wetted perimeter method was used in order to determine the minimum ecological water requirements in the river system. It was found that the current monthly flow rates, with the exception of January to March, are fairly satisfactory. Secondly, an idealised river-lake system was assessed by hydraulics laboratory experimentation and 2D numerical modelling. The experimental and numerical investigations described in this study were undertaken to improve understanding of the hydrdynamic and flushing process within such a river lake system. A water diversion scheme was implemented in order to study lake recharge by river water during dry periods and under augmented flows. Fluorescent tracer experiments and related computer simulations were conducted to assess the performance of different parts of the system before and after implementing the diversion scheme. The results showed that such measures improved flushing, as seen from the perspective of reducing the mean detention time. However, due to poor cross-sectional velocity distribution, recharge alone had little impact on the overall mixing level in the lake waters. The effect of inserting flow deflectors near the lake inlet combined with flow augmentation was then assessed and was found to positively affect the distribution of solutes, by mitigating the occurrence of dead zones. Finally, an eco-hydraulic model was used to determine the levels of fish habitat suitability in the fluvial and lacustrine regions of a new Eco-City. This model has been developed by combining a depth integrated hydrodynamic and water quality model with a Habitat Suitability Index model. Carps were selected as the target species as they represent the major fish population in the study area. Hydrologic data recorded during 2001-2010 were analysed to determine the base flow, average flow and high flow rates, which were used to represent the discharges in the river for the three stages of the carp life cycle: overwintering, spawning and growth, respectively. Numerical model simulations were undertaken to determine the levels of habitat suitability for carps to live at these three life stages. The model results indicated that under the current flow regime the habitat suitability level in the lacustrine region is too low for carps at the growth and overwintering stages. DO depletion, overriding the role of velocity and depth, was attributed to the poorly suited habitat conditions in the lacustrine region. To improve the suitability conditions in the lacustrine region, a DO enhancement scheme was used. Model results showed that the scheme has significantly enhanced the water quality in the lacustrine region. Due to the high flow requirement for carps to spawn in the fluvial region, further numerical model simulations were undertaken to investigate the effect of flow augmentation on the carp spawning habitat suitability

Conservation of tigerfish, Hydrocynus vittatus, in the Kruger National Park with the emphasis on establishing the suitability of the water quantity and quality requirements for the Olifants and Luvuvhu rivers

Hydrocynus vittatus Castelnau, 1861, commonly known as tigerfish, is a flagship species widely distributed in the North Eastern region of South Africa, and are easily identified by the public. This species is actively targeted and utilised by angling and subsistence fishing communities and also used as indicator species by resource and water quality managers to transfer ecosystem related information to the public. Tigerfish therefore has a high ecological, economical and social value to South Africans. Unfortunately, they are lost through habitat changes caused by water extraction, pollution and obstructions like dams and weirs. Tigerfish depend greatly on the available natural habitats to breed, feed and function appropriately. A slight change in the environment may cause depletion of the overall population. Tigerfish are considered rare in South Africa and are classified as a protected species. Scientific studies of all aspects of tigerfish biology are therefore vitally important to understand what quality habitat is required for its successful survival. This information is necessary to development a conservation plan for tigerfish in South Africa. The ecological and economic importance and current conservation status of the tigerfish lead to the current project undertaken by researchers from the Centre for Aquatic Research (CAR) in the Department of Zoology, University of Johannesburg and Water Research Group (WRG), Unit for Environmental Sciences and Management, North West University. Historically tigerfish were prevalent in all 6 major rivers in the Kruger National Park (KNP) and areas on the western border of the Park. Recent surveys have shown that the distribution of this protected species is drastically reduced. The development of a management strategy to protect tigerfish within the Kruger National Park rivers is therefore of utmost importance. As a top predator tigerfish bio-magnifies pollutants and the risk that these pollutants pose are greater to them than to the lower trophic levels. A single study on metal levels in the Olifants River is the only information on levels of contamination in tigerfish. The levels of organic and inorganic substances together with the information on population structures and reproductive status will provide valuable insight into whether exposure to these contaminants has an influence on the general health of tigerfish populations in the KNP. This study addressed all the factors that might influence the health and conservation status of tigerfish. The upper catchments of all the rivers that run through the KNP are subjected to mining as well as intensive agricultural activities with high contamination potential. This tigerfish project was conducted on request from the KNP Scientific Services who identified the management of tigerfish within the borders of the KNP iv as a conservation priority. The study dealt with questions on the sufficiency of the current ecological water allocation for the Olifants River in terms of aquatic species requirements in the system as well as individual and population health

Aquatic habitat shift assessment in a groundwater-fed semi-arid stream: an investigation into the response of Karoo hydroecology to system variability

From introduction: The subject of biological response to changes in aquatic habitat is one which has been well explored in many regions of the world. Examples include work in south east Spain by Mellado Diaz et al. (2008) and Oliva-Paterna et al. (2003), in western United States of America by Hauer and Lorang (2004), and in West Germany by Meyer et al. (2003). Similarly, a number of studies have been conducted in semi-arid regions, exploring elements such as erosion, climate, lithology and landscape formations (e.g. Boardman et al., 2013; Le Maitre et al., 2007; Meyer et al., 2003). However, apart from the study by Uys (1997), and Uys and O’Keeffe (1997), there is a noticeable lack of literature on aquatic habitat shifts in semi-arid stream systems, despite these systems being recognised for their high natural variability. This study provides a base-level approach to conducting habitat shift assessments in a semi-arid stream system and monitoring the hydroecological responses to system variability

Impacts of Climate Change in Determining the Ecological Reserve

The intermediate and long-term impacts of climate change require evaluation of the adaptive capacity of the riverine ecosystems to pro-mote sustainability. The predicted climate change impacts are the moti-vation behind the current research which targets the knowledge gap of the impacts of climate change on the ecological Reserve (or Ecological Water Requirements [EWR]). In order for the Department of Water and Sanitation (DWS) to meet their mandate to protect aquatic ecosystems, given the constraints of climate change, it is necessary to take cogni-sance of the implications of climate change and to make the necessary adjustments and changes to the ecological Reserve determination methodology. These adjustments will help ensure that sufficient water, at the right time, distributed in the right flow pattern and of adequate quality is provided, so that key ecological processes are sustained, and that biotic communities maintain their health and integrity

Water resources availability in the Caledon River basin : past, present and future

The Caledon River Basin is located on one of the most water-scarce region on the African continent. The water resources of the Caledon River Basin play a pivotal role in socio-economic activities in both Lesotho and South Africa but the basin experiences recurrent severe droughts and frequent water shortages. The Caledon River is mostly used for commercial and subsistence agriculture, industrial and domestic supply. The resources are also important beyond the basin’s boundaries as the water is transferred to the nearby Modder River. The Caledon River is also a significant tributary to the Orange-Senqu Basin, which is shared by five southern African countries. However, the water resources in the basin are under continuous threat as a result of rapidly growing population, economic growth as well as changing climate, amongst others. It is therefore important that the hydrological regime and water resources of the basin are thoroughly evaluated and assessed so that they can be sustainably managed and utilised for maximum economic benefits. Climate change has been identified by the international community as one of the most prominent threats to peace, food security and livelihood and southern Africa as among the most vulnerable regions of the world. Water resources are perceived as a natural resource which will be affected the most by the changing climate conditions. Global warming is expected to bring more severe, prolonged droughts and exacerbate water shortages in this region. The current study is mainly focused on investigating the impacts of climate change on the water resources of the Caledon River Basin. The main objectives of the current study included assessing the past and current hydrological characteristics of the Caledon River Basin under current state of the physical environment, observed climate conditions and estimated water use; detecting any changes in the future rainfall and evaporative demands relative to present conditions and evaluating the impacts of climate on the basin’s hydrological regime and water resources availability for the future climate scenario, 2046-2065. To achieve these objectives the study used observed hydrological, meteorological data sets and the basin’s physical characteristics to establish parameters of the Pitman and WEAP hydrological models. Hydrological modelling is an integral part of hydrological investigations and evaluations. The various sources of uncertainties in the outputs of the climate and hydrological models were identified and quantified, as an integral part of the whole exercise. The 2-step approach of the uncertainty version of the model was used to estimate a range of parameters yielding behavioural natural flow ensembles. This approach uses the regional and local hydrological signals to constrain the model parameter ranges. The estimated parameters were also employed to guide the calibration process of the Water Evaluation And Planning (WEAP) model. The two models incorporated the estimated water uses within the basin to establish the present day flow simulations and they were found to sufficiently simulate the present day flows, as compared to the observed flows. There is an indication therefore, that WEAP can be successfully applied in other regions for hydrological investigations. Possible changes in future climate regime of the basin were evaluated by analysing downscaled temperature and rainfall outputs from a set of 9 climate models. The predictions are based on the A2 greenhouse gases emission scenario which assumes a continuous increase in emission rates. While the climate models agree that temperature, and hence, evapotranspiration will increase in the future, they demonstrate significant disagreement on whether rainfall will decrease or increase and by how much. The disagreement of the GCMs on projected future rainfall constitutes a major uncertainty in the prediction of water resources availability of the basin. This is to the extent that according to 7 out of 9 climate models used, the stream flow in four sub-basins (D21E, D22B, D23D and D23F) in the Caledon River Basin is projected to decrease below the present day flows, while two models (IPSL and MIUB) consistently project enhanced water resource availability in the basin in the future. The differences in the GCM projections highlight the margin of uncertainty involved predicting the future status of water resources in the basin. Such uncertainty should not be ignored and these results can be useful in aiding decision-makers to develop policies that are robust and that encompass all possibilities. In an attempt to reduce the known uncertainties, the study recommends upgrading of the hydrological monitoring network within the Caledon River Basin to facilitate improved hydrological evaluation and management. It also suggests the use of updated climate change data from the newest generation climate models, as well as integrating the findings of the current research into water resources decision making process

Deployment, Maintenance And Further Development Of Spatsim-HDSF Volume

The National Water Act (NWA, 1998) of South Africa (Act 36 of 1998) aims to ensure that South Africa’s water resources are managed and used in an equitable and sus-tainable manner for the benefit of all. The National Water Act (NWA) requires a dif-ferent approach to managing the nation’s water resources and the concept of inte-grated water resources management (IWRM) is central to this approach (Pollard and Du Toit, 2008). IWRM requires water managers to consider hydrological, ecological, economic, political, social and institutional aspects of water resources. To imple-ment IWRM, water managers require integrated modelling tools to provide infor-mation that can assist in making managements decisions. There are two aspects of integrated modelling that have received increasing attention in recent years: (i) the coupling of models representing different water resource domains, and (ii) the de-velopment of integrated modelling frameworks or decision support systems. These integrated modelling frameworks typically include a common data repository, common data editing tools, common spatial and temporal data visualisation and analysis tools, and a collection of framework compatible models that make use of these common tools

Development of a hydraulic sub-model as part of a desktop environmental flow assessment method

Countries around the world have been developing ecological policies to protect their water resources and minimise the impacts of development on their river systems. The concept of ‘minimum flows’ was initially established as a solution but it did not provide sufficient protection as all elements of a flow regime were found to be important for the protection of the river ecosystem. “Environmental flows” were developed to determine these flow regimes to maintain a river in some defined ecological condition. Rapid, initial estimates of the quantity component of environmental flows may be determined using the Desktop Reserve Model in South Africa. However, the Desktop Reserve Model is dependent upon the characteristics of the reference natural hydrology used. The advancements in hydraulic and ecological relationships from the past decade have prompted the development of a Revised Desktop Reserve Model (RDRM) that would incorporate these relationships. The research in this thesis presents the development of the hydraulic sub-model for the RDRM. The hydraulic sub-model was designed to produce a realistic representation of the hydraulic conditions using hydraulic parameters/characteristics from readily available information for any part of South Africa. Hydraulic data from past EWR studies were used to estimate the hydraulic parameters. These estimated hydraulic parameters were used to develop hydraulic estimation relationships and these relationships were developed based on a combination of regression and rule-based procedures. The estimation relationships were incorporated into the hydraulic sub-model of the integrated RDRM and assessments of the hydraulic outputs and EWR results were undertaken to assess the ‘applicability’ of the hydraulic sub-model. The hydraulic sub-model was assessed to be at a stage where it can satisfactorily be incorporated in the RDRM and that it is adequately robust in many situations. Recommendations for future work include the refinement of estimation of the channel forming discharge or the use of spatial imagery to check the maximum channel width estimation. It is also proposed that a future version of the hydraulic sub-model could include flow regime change impacts on channel geomorphology and sedimentology so that flow management scenarios can be more effectively assessed

An assessment of instream flow requirements in the Sabie-Sand River catchment

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. February 2015.This dissertation is an assessment of the compliance with and performance of the Instream Flow Requirement (IFR) system and the Building Block Methodology for the Sabie-Sand River. Firstly, a comprehensive exploration of aspects of the ecological system in the Sabie-Sand Catchment is set out and explored in an attempt to garner an understanding of the pertinent ecological components of the river, in the form of a literature review. This is done with a view to gaining insight into where potential ecological failure may occur should flows in the Sabie-Sand be inadequate for ecological maintenance. A range of abiotic and biotic factors are investigated, and the manner in which they might change in response to changing flow conditions is set out