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Papers by Pieter van der Zaag

Water

The process of development has led to the modification of river landscapes. This has created imba... more The process of development has led to the modification of river landscapes. This has created imbalances between ecological, economic, and socio-cultural uses of ecosystem services (ESs), threatening the biotic and social integrity of rivers. Anthropogenic modifications influence river landscapes on multiple scales, which impact river-flow regimes and thus the production of river ESs. Despite progress in developing approaches for the valuation ecosystem goods and services, the ecosystem service research fails to acknowledge the biophysical structure of river landscape where ecosystem services are generated. Therefore, the purpose of this review is to synthesize the literature to develop the understanding of the biocomplexity of river landscapes and its importance in ecosystem service research. The review is limited to anthropogenic modifications from catchment to reach scale which includes inter-basin water transfer, change in land-use pattern, sub-surface modifications, groundwater ...

Atmosphere

Globally, freshwater resources are threatened, resulting in challenges for urban water supply and... more Globally, freshwater resources are threatened, resulting in challenges for urban water supply and management. Climate change, population growth, and urbanization have only exacerbated this crisis. For the Caribbean, climate change through the impact of increasing temperatures and rainfall variability has resulted in more frequent and intense episodes of disasters including droughts and floods which have impaired the quantity and quality of freshwater supplies. Using Caribbean-specific climate forecasting, it is shown that rainfall totals in Kingston, Jamaica, are expected to reduce by 2030 and 2050 under two RCPs. In addition, the timing of the primary rainy season is expected to shift, potentially impacting water supply security. Analysis of the potential of rainwater harvesting (RWH) to augment supply and enhance water supply resilience shows that in two communities studied in Kingston, it can contribute up to 7% of total water supply. Household storage requirements are about 1 m3...

Hydrological Sciences Journal

Water Policy

The water resources of the Incomati river basin, shared between South Africa, Swaziland and Mozam... more The water resources of the Incomati river basin, shared between South Africa, Swaziland and Mozambique, are intensively used. Moreover, the basin is situated in a part of Africa that over the last 40 years has experienced a dynamic, sometimes turbulent and volatile, political history. Both ingredients might have been sufficient for the emergence of confrontations over water. Tensions between Mozambique, South Africa and Swaziland over Incomati waters existed but never escalated. This case study attempts to explain why cooperation prevailed, by presenting information about the natural characteristics of the basin, its political history, water developments and the negotiations that took place during the period 1967–2002. The paper provides four explanations why tensions did not escalate and cooperation prevailed. It is concluded that the developments in the Incomati basin support the hypothesis that water drives peoples and countries towards cooperation. Increased water use has indeed...

Water

The variability of rainfall and climate, combined with land use and land cover changes, and varia... more The variability of rainfall and climate, combined with land use and land cover changes, and variation in geology and soils makes it a difficult task to accurately describe the key hydrological processes in a catchment. With the aim to better understand the key hydrological processes and runoff generation mechanisms in the semi-arid meso-scale Kaap catchment in South Africa, a hydrological model was developed using the open source STREAM model. Dominant runoff processes were mapped using a simplified Height Above the Nearest Drainage approach combined with geology. The Prediction in Ungauged Basins (PUB) framework of runoff signatures was used to analyse the model results. Results show that in the headwater sub-catchments of Noordkaap and Suidkaap, plateaus dominate, associated with slow flow processes. Therefore, these catchments have high baseflow components and are likely the main recharge zone for regional groundwater in the Kaap. In the Queens sub-catchment, hillslopes associate...

Physics and Chemistry of the Earth, Parts A/B/C

ABSTRACT If the future availability of water is uncertain to water managers, dam operators and wa... more ABSTRACT If the future availability of water is uncertain to water managers, dam operators and water users, then an effective allocation among competing uses can be difficult. The difficulties can partly be alleviated by including streamflow forecasting as a tool for informed decision making. The Incomati basin in Southern Africa frequently experiences water shortages, and here streamflow forecasting can contribute to an improved water management. This paper explores the skill of streamflow forecasting and its usefulness in decision making in the Incomati basin. The study applies correlation and regression methods to forecast streamflow, and standard verification scores to evaluate the skill of the forecasts. Suitable statistical forecasting techniques were analysed and tested. The data used for forecasting include Sea Surface Temperature (SST), El Niño Southern Oscillation (ENSO), rainfall and streamflow. Results show that there is some scope for streamflow forecasting that can support water management decision making in the basin. The rainfall and streamflow of the previous months and/or season can be used to predict the streamflow in the next month and/or season with reasonable to good results. Results obtained during low flow periods (May-September) were found to be better than those obtained for the high flow periods (October-April). However, inclusion of ENSO and/or SST as an explanatory variable enhanced forecast skill, particularly during high flow periods. Forecasts were conducted for streamflow being in the below normal, above normal or normal terciles, with the forecasts for the extremes found to have better skill than forecast for the sreamflow being in the normal tercile. Forecasts for low flows demonstrated the best skills, with these being of most use to the allocation of the scarce water resources.

Journal of environmental management, Jan 15, 2017

Crowd-sourced environmental observations are increasingly being considered as having the potentia... more Crowd-sourced environmental observations are increasingly being considered as having the potential to enhance the spatial and temporal resolution of current data streams from terrestrial and areal sensors. The rapid diffusion of ICTs during the past decades has facilitated the process of data collection and sharing by the general public and has resulted in the formation of various online environmental citizen observatory networks. Online amateur weather networks are a particular example of such ICT-mediated observatories that are rooted in one of the oldest and most widely practiced citizen science activities, namely amateur weather observation. The objective of this paper is to introduce a conceptual framework that enables a systematic review of the features and functioning of these expanding networks. This is done by considering distinct dimensions, namely the geographic scope and types of participants, the network's establishment mechanism, revenue stream(s), existing communi...

Examining Underexplored Dimensions, 2009

Phys Chem Earth, 2008

... different uses of water at all levels within and between states through sustainable rivermana... more ... different uses of water at all levels within and between states through sustainable rivermanagement. ... environmental and cultural values for all its uses (and to move to pricing water services to ... and the interests of stakeholders are included in the management of water resources. ...

Http Dx Doi Org 10 1080 02508060 2013 791763, May 1, 2013

Irrigation and Drainage Systems, 1993

Sand rivers and sand dams offer an alternative to conventional surface water reservoirs for stora... more Sand rivers and sand dams offer an alternative to conventional surface water reservoirs for storage. The alluvial aquifers that make up the beds of sand rivers can store water with minimal evaporation (extinction depth is 0.9 m) and natural filtration. The alluvial aquifers of the Mzingwane Catchment are the most extensive of any tributaries in the Limpopo Basin. The lower Mzingwane aquifer, which is currently underutilised, is recharged by managed releases from Zhovhe Dam (capacity 133 Mm3). The volume of water released annually is only twice the size of evaporation losses from the dam; the latter representing nearly one third of the dam's storage capacity. The Lower Mzingwane valley currently support commercial agro-businesses (1,750 ha irrigation) and four smallholder irrigation schemes (400 ha with provision for a further 1,200 ha). In order to support planning for optimising water use and storage over evaporation and to provide for more equitable water allocation, the spreadsheet-based balance model WAFLEX was used. It is a simple and userfriendly model, ideal for use by institutions such as the water management authorities in Zimbabwe which are challenged by capacity shortfalls and inadequate data. In this study, WAFLEX, which is normally used for accounting the surface water balance, is adapted to incorporate alluvial aquifers into the water balance, including recharge, baseflow and groundwater flows. Results of the WAFLEX modelling suggest that there is surplus water in the lower Mzingwane system, and thus there should not be any water conflicts. Through more frequent timing of releases from the dam and maintaining the alluvial aquifers permanently saturated, less evaporation losses will occur in the system and the water resources can be better shared to provide more irrigation water for smallholder farmers in the highly resource-poor communal lands along the river. Sand dams are needed to augment the aquifer storage system and improve access to water. An alternative to the current scenario was modelled in WAFLEX: making fuller use of the alluvial aquifers upstream and downstream of Zhovhe Dam. These alluvial aquifers have an estimated average water storage capacity of 0.37 Mm3 km

Historically, civilizations have developed around rivers and river basins. In the past century, a... more Historically, civilizations have developed around rivers and river basins. In the past century, a particular model of river basin development has tended to dominate planning and policy making. This is the model of developing river basins through large, centralized storages in the form of a dam, connected to a network of man-made canals and hydraulic infrastructure to harness the run-off from catchment areas. Such a model requires large investments of capital and high technical skills to construct and maintain and is usually financed and ...

Water

The process of development has led to the modification of river landscapes. This has created imba... more The process of development has led to the modification of river landscapes. This has created imbalances between ecological, economic, and socio-cultural uses of ecosystem services (ESs), threatening the biotic and social integrity of rivers. Anthropogenic modifications influence river landscapes on multiple scales, which impact river-flow regimes and thus the production of river ESs. Despite progress in developing approaches for the valuation ecosystem goods and services, the ecosystem service research fails to acknowledge the biophysical structure of river landscape where ecosystem services are generated. Therefore, the purpose of this review is to synthesize the literature to develop the understanding of the biocomplexity of river landscapes and its importance in ecosystem service research. The review is limited to anthropogenic modifications from catchment to reach scale which includes inter-basin water transfer, change in land-use pattern, sub-surface modifications, groundwater ...

Atmosphere

Globally, freshwater resources are threatened, resulting in challenges for urban water supply and... more Globally, freshwater resources are threatened, resulting in challenges for urban water supply and management. Climate change, population growth, and urbanization have only exacerbated this crisis. For the Caribbean, climate change through the impact of increasing temperatures and rainfall variability has resulted in more frequent and intense episodes of disasters including droughts and floods which have impaired the quantity and quality of freshwater supplies. Using Caribbean-specific climate forecasting, it is shown that rainfall totals in Kingston, Jamaica, are expected to reduce by 2030 and 2050 under two RCPs. In addition, the timing of the primary rainy season is expected to shift, potentially impacting water supply security. Analysis of the potential of rainwater harvesting (RWH) to augment supply and enhance water supply resilience shows that in two communities studied in Kingston, it can contribute up to 7% of total water supply. Household storage requirements are about 1 m3...

Hydrological Sciences Journal

Water Policy

The water resources of the Incomati river basin, shared between South Africa, Swaziland and Mozam... more The water resources of the Incomati river basin, shared between South Africa, Swaziland and Mozambique, are intensively used. Moreover, the basin is situated in a part of Africa that over the last 40 years has experienced a dynamic, sometimes turbulent and volatile, political history. Both ingredients might have been sufficient for the emergence of confrontations over water. Tensions between Mozambique, South Africa and Swaziland over Incomati waters existed but never escalated. This case study attempts to explain why cooperation prevailed, by presenting information about the natural characteristics of the basin, its political history, water developments and the negotiations that took place during the period 1967–2002. The paper provides four explanations why tensions did not escalate and cooperation prevailed. It is concluded that the developments in the Incomati basin support the hypothesis that water drives peoples and countries towards cooperation. Increased water use has indeed...

Water

The variability of rainfall and climate, combined with land use and land cover changes, and varia... more The variability of rainfall and climate, combined with land use and land cover changes, and variation in geology and soils makes it a difficult task to accurately describe the key hydrological processes in a catchment. With the aim to better understand the key hydrological processes and runoff generation mechanisms in the semi-arid meso-scale Kaap catchment in South Africa, a hydrological model was developed using the open source STREAM model. Dominant runoff processes were mapped using a simplified Height Above the Nearest Drainage approach combined with geology. The Prediction in Ungauged Basins (PUB) framework of runoff signatures was used to analyse the model results. Results show that in the headwater sub-catchments of Noordkaap and Suidkaap, plateaus dominate, associated with slow flow processes. Therefore, these catchments have high baseflow components and are likely the main recharge zone for regional groundwater in the Kaap. In the Queens sub-catchment, hillslopes associate...

Physics and Chemistry of the Earth, Parts A/B/C

ABSTRACT If the future availability of water is uncertain to water managers, dam operators and wa... more ABSTRACT If the future availability of water is uncertain to water managers, dam operators and water users, then an effective allocation among competing uses can be difficult. The difficulties can partly be alleviated by including streamflow forecasting as a tool for informed decision making. The Incomati basin in Southern Africa frequently experiences water shortages, and here streamflow forecasting can contribute to an improved water management. This paper explores the skill of streamflow forecasting and its usefulness in decision making in the Incomati basin. The study applies correlation and regression methods to forecast streamflow, and standard verification scores to evaluate the skill of the forecasts. Suitable statistical forecasting techniques were analysed and tested. The data used for forecasting include Sea Surface Temperature (SST), El Niño Southern Oscillation (ENSO), rainfall and streamflow. Results show that there is some scope for streamflow forecasting that can support water management decision making in the basin. The rainfall and streamflow of the previous months and/or season can be used to predict the streamflow in the next month and/or season with reasonable to good results. Results obtained during low flow periods (May-September) were found to be better than those obtained for the high flow periods (October-April). However, inclusion of ENSO and/or SST as an explanatory variable enhanced forecast skill, particularly during high flow periods. Forecasts were conducted for streamflow being in the below normal, above normal or normal terciles, with the forecasts for the extremes found to have better skill than forecast for the sreamflow being in the normal tercile. Forecasts for low flows demonstrated the best skills, with these being of most use to the allocation of the scarce water resources.

Journal of environmental management, Jan 15, 2017

Crowd-sourced environmental observations are increasingly being considered as having the potentia... more Crowd-sourced environmental observations are increasingly being considered as having the potential to enhance the spatial and temporal resolution of current data streams from terrestrial and areal sensors. The rapid diffusion of ICTs during the past decades has facilitated the process of data collection and sharing by the general public and has resulted in the formation of various online environmental citizen observatory networks. Online amateur weather networks are a particular example of such ICT-mediated observatories that are rooted in one of the oldest and most widely practiced citizen science activities, namely amateur weather observation. The objective of this paper is to introduce a conceptual framework that enables a systematic review of the features and functioning of these expanding networks. This is done by considering distinct dimensions, namely the geographic scope and types of participants, the network's establishment mechanism, revenue stream(s), existing communi...

Examining Underexplored Dimensions, 2009

Phys Chem Earth, 2008

... different uses of water at all levels within and between states through sustainable rivermana... more ... different uses of water at all levels within and between states through sustainable rivermanagement. ... environmental and cultural values for all its uses (and to move to pricing water services to ... and the interests of stakeholders are included in the management of water resources. ...

Http Dx Doi Org 10 1080 02508060 2013 791763, May 1, 2013

Irrigation and Drainage Systems, 1993

Sand rivers and sand dams offer an alternative to conventional surface water reservoirs for stora... more Sand rivers and sand dams offer an alternative to conventional surface water reservoirs for storage. The alluvial aquifers that make up the beds of sand rivers can store water with minimal evaporation (extinction depth is 0.9 m) and natural filtration. The alluvial aquifers of the Mzingwane Catchment are the most extensive of any tributaries in the Limpopo Basin. The lower Mzingwane aquifer, which is currently underutilised, is recharged by managed releases from Zhovhe Dam (capacity 133 Mm3). The volume of water released annually is only twice the size of evaporation losses from the dam; the latter representing nearly one third of the dam's storage capacity. The Lower Mzingwane valley currently support commercial agro-businesses (1,750 ha irrigation) and four smallholder irrigation schemes (400 ha with provision for a further 1,200 ha). In order to support planning for optimising water use and storage over evaporation and to provide for more equitable water allocation, the spreadsheet-based balance model WAFLEX was used. It is a simple and userfriendly model, ideal for use by institutions such as the water management authorities in Zimbabwe which are challenged by capacity shortfalls and inadequate data. In this study, WAFLEX, which is normally used for accounting the surface water balance, is adapted to incorporate alluvial aquifers into the water balance, including recharge, baseflow and groundwater flows. Results of the WAFLEX modelling suggest that there is surplus water in the lower Mzingwane system, and thus there should not be any water conflicts. Through more frequent timing of releases from the dam and maintaining the alluvial aquifers permanently saturated, less evaporation losses will occur in the system and the water resources can be better shared to provide more irrigation water for smallholder farmers in the highly resource-poor communal lands along the river. Sand dams are needed to augment the aquifer storage system and improve access to water. An alternative to the current scenario was modelled in WAFLEX: making fuller use of the alluvial aquifers upstream and downstream of Zhovhe Dam. These alluvial aquifers have an estimated average water storage capacity of 0.37 Mm3 km

Historically, civilizations have developed around rivers and river basins. In the past century, a... more Historically, civilizations have developed around rivers and river basins. In the past century, a particular model of river basin development has tended to dominate planning and policy making. This is the model of developing river basins through large, centralized storages in the form of a dam, connected to a network of man-made canals and hydraulic infrastructure to harness the run-off from catchment areas. Such a model requires large investments of capital and high technical skills to construct and maintain and is usually financed and ...