Exploratory use of a Bayesian network process for translating stakeholder perceptions of water quality problems in a catchment in South Africa

Water resource management is complex, and should ideally be a co-operative, stakeholder-driven  problem-solving process. Bayesian networks (BNs) are one participatory tool being increasingly used  to  facilitate this process. The upper Mgeni catchment in the province of KwaZulu-Natal, South Africa, is a key water resource area with looming water quality problems. The high number of stakeholders involved in a catchment management forum provided an environment for testing the development of a BN showing relationships between water quality problems and stakeholders in this area. Through  engagement with stakeholders at quarterly meetings during 2011, and collation and analysis of water quality time-series, qualitative and quantitative data were successfully translated into a BN for water quality improvement in the study area. The model demonstrated that certain water quality variables (for example, compliance of wastewater treatment works; increase in housing developments) were more likely to be the cause of problems than others (such as discharges from farm dams or accidental spills). The value of involving stakeholders in a co-operative process is highlighted, and it is argued that the robustness of such a model would be enhanced further if applied within a formal participatory approach using conditional probability values endorsed by all stakeholders.Keywords: catchment management, land use, probability, stakeholder engagement, water qualit

Current concept of abdominal sepsis : WSES position paper

Peer reviewe

2013 WSES guidelines for management of intra-abdominal infections

Peer reviewe

Intra-annual thermal patterns in the main rivers of the Sabie Catchment, Mpumalanga, South Africa

Water temperatures serve as indices of catchment condition, being a function of a multitude of variables acting as both drivers and buffers, at different temporal and spatial scales. Data loggers were used to record time series of hourly water temperatures within the Sabie, Sand and Marite Rivers of the Sabie catchment, Mpumalanga, South Africa. Two years of hourly water temperatures were scaled up to provide daily statistics of water temperatures, which provided information on intra-annual thermal variability as well as how this changed along the longitudinal axis of the Sabie River. In general, mean and maximum water temperatures, and thermal variability, increased with downstream distance in the Sabie River. Water temperatures in the two main tributaries of the Sabie River, viz. the Marite and Sand Rivers, displayed higher maxima and lower minima than corresponding sites in the Sabie River. Further research on the role of hyporheic water and the contribution of tributaries is proposed, together with additional long-term collection of water temperature time series. Key Words: Water temperatures, Sabie River, Intra-annual variability WaterSA Vol.30(4) 2004: 445-45

A regional flow type classification for South African perennial rivers

Flow classification provides a statistically robust method of defining an expected range of variability for flow metrics describing frequency, magnitude, duration and timing of events.  Here, we characterised reference mean daily flows for 1950–1999 for all 5 838 quinary catchments of South Africa based on 150 metrics.  Using a two-tiered approach, where sub-catchments were classified into similar flow types using principal components and cluster analyses, we defined 6 to 12 flow types for each of 8 hydrological regions reflecting rainfall seasonality.  Redundancy between variables was 87% on average, so that site variability could be accounted for using 8–28 metrics.  In general, flow volume metrics accounted for Axis 1 variability, while coefficients of dispersion had 1.8 times less leverage in Axis 2.  With the incorporation into a spatial product and an associated database, this study provides a basis for defining statistically robust reference flow conditions for multiple flow metrics, against which current observed flows at specific sites may be compared

Derivation of quantitative management objectives for annual instream water temperatures in the Sabie River using a biological index

No Abstract. Water SA Vol. 31(4) 2005: 473-48

Use of biological and water quality indices to evaluate conditions of the Upper uMngeni Catchment, KwaZulu-Natal, South Africa

Urban and agricultural land uses have the potential to severely compromise the quality of impoundments, if ineffectively managed and operated. A case in point is the upper uMngeni Catchment, including Midmar Dam, which is integral to the freshwater supply infrastructure in KwaZulu-Natal, South Africa. Monitoring sites were established in varying land use types in three subcatchments of the upper uMngeni Catchment to assess water quality and ecosystem health impacts of current land uses. Conclusions about water quality were drawn using pairing of SASS5 and spot water quality data. Water quality and ecological condition were highest in commercial plantations and upstream of a high-density settlement where natural land cover and sparse settlement occurred. Although marked declines in water quality and ecological condition were observed under commercial agriculture. The most notable declines in water quality and ecological condition were observed downstream of the settlement with elevated nutrient loads. Shifts in aquatic biota were highly correlated with seasonal shifts in water quality, influenced markedly by land use. The cumulative effects of current land use activities, urban development and agriculture on Midmar Dam’s water quality should be viewed with concern. Additional development in the form of additional social housing projects may exacerbate impacts.&nbsp