Climate change and socio-hydrological dynamics: Adaptation and feedbacks

Published ArticleA functioning ecological system results in ecosystem goods and services which are of direct value to human beings. Ecosystem services are the conditions and processes which sustain and fulfil human life, and maintain biodiversity and the production of ecosystem goods. However, human actions affect ecological systems and the services they provide through various activities, such as land use, water use, pollution and climate change. Climate change is perhaps one of the most important sustainable development challenges that threatens to undo many of the development efforts being made to reach the targets set for the Millennium Development Goals. Understanding the provision of ecosystem services and how they change under different scenarios of climate and biophysical conditions could assist in bringing the issue of ecosystem services into decision making process. Similarly, the impacts of land use change on ecosystems and biodiversity have received considerable attention from ecologists and hydrologists alike. Land use change in a catchment can impact on water supply by altering hydrological processes, such as infiltration, groundwater recharge, base flow and direct runoff. In the past a variety of models were used for predicting landuse changes. Recently, the focus has shifted away from using mathematically oriented models to agent-based modeling (ABM) approach to simulate land use scenarios. The agent-based perspective, with regard to land-use cover change, is centered on the general nature and rules of land-use decision making by individuals. A conceptual framework is developed to investigate the possibility of incorporating the human dimension of land use decision and climate change model into a hydrological model in order to assess the impact of future land use scenario and climate change on the ecological system in general and water resources in particular. Climate change and socio-hydrological dynamics: Adaptation and feedbacks (PDF Download Available). Available from: https://www.researchgate.net/publication/260024549_Climate_change_and_socio-hydrological_dynamics_Adaptation_and_feedbacks [accessed Jan 14, 2016]

Spatiotemporal analysis of droughts using self-calibrating Palmer’s Drought Severity Index in the central region of South Africa

Published ArticleThe loss of life and property from drought events has forced society to focus on the development of reliable early warning systems which may enable farmers and other stakeholders to correctly and timely adapt to the expected impacts of climatic hazard. However, a scientific approach to a reliable early warning system for a region requires, among others, characterisation of drought events in the region in terms of duration, magnitude, intensity and frequency using standard drought indices. Therefore, the objective of this study was to identify and characterise drought events in the Modder River basin, central region of South Africa, using a self-calibrated Palmer’s Drought Severity Index (sc-PDSI). Attempts were also made to establish a relationship between meteorological and hydrological drought events in the region. During the period of analysis, the total number of drought episodes identified in the study area ranged between eight and sixteen. It was found that the most severe drought episodes occurred during the period 1992–1995 followed by the period 1982–1987. Results of analysis of seasonal drought events in one of the quaternary catchments (C52A) revealed that peak drought events during the three summer months (November, December and January) occurred in the area in 1993. However, in terms of event magnitude and intensity, the worst drought events were recorded during the period December 1982–July 1987, followed by the event that ensued during December 1989–September 1995. Results of analysis of decadal variation of drought events showed that the number of extreme and moderate drought events recorded in the catchment showed statistically significant increasing trends during the five decades at 5 % significance level. Moreover, spectral analysis of sc-PDSI time series in the region identified periodicities in the time series ranging from 6 years (C52E) to 16 years (C52K). In terms of the spatial extent of extreme drought events, the maximum areal coverage (91 %) was recorded in November 1998, followed by December 1998 and December–January 1999 (43 %). Analysis of the relative frequency of droughts of varying categories revealed that extreme drought events were most prevalent in the C52E (2.72 %) quaternary catchment, followed by C52C (2.21 %). The study also found an average lag time of 10 months between the onsets of meteorological and hydrological drought events in the region

Assessment Of Localized Seasonal Precipitation Variability In The Upper Middle Catchment Of The Olifants River Basin

ArticleThis study used the Soil and Water Assessment Tool (SWAT) model together with regional climate downscaled (RCD) data from the CORDEX (Africa project), to assess the local seasonal precipitation variability in the upper middle catchment (UMC) of the Olifants River basin. The study results, based on two scenarios (RCP4.5 and RCP8.5), showed a wider monthly and seasonal variability of precipitation. The study also indicated a strong decreasing trend of east-to-west direction of spatial precipitation, with most precipitation concentrated in the eastern part of the study area. Within the western part of the UMC, we also noted another decreasing trend of precipitation from south-tonorth with northern areas of the study area receiving the least amount of precipitation. This study has also revealed a considerable general reduction of future seasonal precipitation especially in the mid-term period (2021–2050). The general reduction in future seasonal precipitation, combined with the increasing temperatures in the area, may exacerbate the drought conditions and reduction in streamflow of the main river (Olifants) and its tributaries, consequently having a negative impact on the economic activities in the basin

Assessment of localized seasonal precipitation variability in the upper middle catchment of the Olifants River basin

Abstract: This study used the Soil and Water Assessment Tool (SWAT) model together with regional climate downscaled (RCD) data from the CORDEX (Africa project), to assess the local seasonal precipitation variability in the upper middle catchment (UMC) of the Olifants River basin. The study results, based on two scenarios (RCP4.5 and RCP8.5), showed a wider monthly and seasonal variability of precipitation. The study also indicated a strong decreasing trend of east-to-west direction of spatial precipitation, with most precipitation concentrated in the eastern part of the study area. Within the western part of the UMC, we also noted another decreasing trend of precipitation from south-tonorth with northern areas of the study area receiving the least amount of precipitation. This study has also revealed a considerable general reduction of future seasonal precipitation especially in the mid-term period (2021–2050). The general reduction in future seasonal precipitation, combined with the increasing temperatures in the area, may exacerbate the drought conditions and reduction in streamflow of the main river (Olifants) and its tributaries, consequently having a negative impact on the economic activities in the basin

Techniques for Calibration and Validation of SWAT Model in Data Scarce Arid and Semi-Arid Catchments in South Africa

Published ArticleStudy region: This study was conducted in Soutloop River Catchment, Northern Cape, South Africa. Study focus: Although hydrologic models play a critical role in the management of natural resources in arid areas, their application is challenged by the scarcity of data for calibration and validation. Therefore, this study aimed at to configure, calibrate and validate SWAT model in a data-scarce catchment by using the regionalization with physical similarity approach. This approach uses dual calibration and validation procedure, i.e., one in the donor catchment (by using SWAT-CUP (SWAT Calibration and Uncertainty Programs) and the other on the study catchment (by manual calibration and verification). New hydrological insights for the region: Based on the sensitivity analysis, sixteen parameters were calibrated by SWAT-CUP. The result from the uncertainty analysis indicated acceptable values of both the R-factor (0.8**) and P-factor (0.7**). The model performance evaluation also showed acceptable ranges of values (e.g., NS was 0.76** and R2 was 0.78**). However, the main calibration and validation process was conducted outside the target catchment, though it was assumed that the donor and target catchments have similar hydrological responses. Therefore, the study suggested further inspection methods to minimize the model uncertainty in the study catchment. This study enables researchers to exploit the river eco-regional classifications of South Africa to apply hydrologic models to estimate the components of water balance in arid/ semi-arid catchments

Analysis of Droughts in the Central Region of South Africa and Their Association with SST Anomalies

The objective of this study was to characterise meteorological droughts in the Central Region of South Africa using Standardised Precipitation Evapotranspiration Index (SPEI) and to examine if there is a relationship between drought and El Niño events. The SPEI was used to quantify the precipitation deficit over time and space across the catchment for the time-scales that are important for planning and management of water resources. Based on 12-month time-scale, the total number of drought events identified in the area using SPEI ranged between 13 and 20 during the period of analysis (1952–1999). Considering the effects of event magnitude and duration as severity parameters, the most severe drought event was identified during 1973 followed by 1995 based on 12-month time-scale. Moreover, it was also found that the number of moderate, severe, and extreme drought events identified by SPEI follows increasing trend with decade during the period of analysis. Results of Spearman’s rank correlation test revealed that the trends exhibited by mild (SPEI-3 and SPEI-6), moderate (SPEI-12), severe (SPEI-12), and extreme (SPEI-3) drought categories are statistically significant at 5% significance level. The study also revealed that drought events in the central region of South Africa are preceded by El Niño events in the tropical Pacific (Nino 3.4) with an average lag time of 8 months between the onsets of the two events. It was found that hydrological drought events in the study area lag behind meteorological drought events with an average lag time of 7.4 months. Findings of this study can be used to forecast drought events in the area for the proper planning and management of water resources

Analysis of the Spatio-Temporal Variability of Precipitation and Drought Intensity in an Arid Catchment in South Africa

Water deficit is high and precipitation varies spatio-temporally in arid areas. This study was conducted to analyse the spatio-temporal variability of precipitation and drought intensity in an arid catchment in South Africa. The Soil and Water Assessment Tool (SWAT) was used to estimate the spatio-temporal precipitation where nine meteorological stations were used as input to the model. The model was calibrated and validated by regionalization with a physical similarity approach. SWAT only predicts precipitation at sub-basin level. Hence, the mean precipitation was further interpolated by using the inverse distance weighted method (IDW). The Mann–Kendall trend test shows that there was no trend in annual precipitation whereas in the monthly precipitation there was a 0.01 mm decrease. Daily precipitation varied from 0.1 to 4 mm whereas in a monthly basis, it varied from 6 mm (September) to 43.4 mm (February). The annual precipitation varied from 169 mm (1983) to 415 mm (2003) with a long-term mean of 280.8 mm. Precipitation is also highly variable in space throughout the catchment. Generally, annual precipitation decreased from north to south; however, during the winter season, the reverse was true due to the influence of rain-bearing condition from the south- western direction. Based on the aridity index (AI), the catchment is categorized as arid. The SPI shows that the 1983 drought was the worst whereas the 2003 and 2004 years were relatively wet. The results from this study provide baseline information for further research in climate change adaptation and environmental monitoring programs in the region