Bulk Water Supply Research Articles

The Role of Effective Planning on Performance of Kigali Bulk Water Supply Project in Kanzenze Cell in Bugesera District, Rwanda

The Role of Effective Planning on Performance of Kigali Bulk Water Supply Project in Kanzenze Cell in Bugesera District, Rwanda

The migration of aquatic macrocrustaceans over an artificial barrier in the uThukela river, South Africa

AbstractDiadromous macrocrustaceans need connectivity between the ocean, estuary and river to complete their life cycle. Instream barriers in lower reaches of rivers threaten upstream migrations of diadromous macrocrustaceans. Varuna litterata migrate upstream after a spawning event out at sea. These migration events have been poorly documented. We documented the presence V. litterata and Macrobrachium spp. at a vertical slot fishway and a rock ramp on the Lower Thukela River Bulk Water Supply Scheme Weir, KwaZulu‐Natal, South Africa, during 2021–2022. We found Macrobrachium spp. and V. litterata made use of the rock ramp. However, the vertical slot fishway did hinder the migration of V. litterata significantly, as found in other studies.

Sustainability of drinking water and sanitation delivery systems in rural communities of the Lepelle Nkumpi Local Municipality, South Africa.

Water and sanitation are core for the growth and development of communities. Yet, South African local municipalities are often unable to sustainably deliver safe water and basic sanitation for all. Drawing on perspectives of ecological economics, this study analysed the sustainability of water and sanitation systems in rural communities of the Lepelle Nkumpi Local Municipality. Mixed research approach was used to collect the data from 657 household and institutional respondents. The study found that households used water for multi-purposes including consumptive, productive and domestic, but existing facilities are in deplorable condition. Pollution arising from agrochemicals, waste systems, mining, sewerage, and industrial effluence significantly affected water systems in the communities. Bridging demand-supply gaps require initiatives like bulk water supply and implementation of the free basic water policy in underprivileged areas. Tariffs should either be waived or adjusted for extremely poor households. Waste management initiatives, like capacity building, public education, investments, and facility upgrade, could help avert spread of waterborne infections and improve the resident's health.

Evaluasi Risiko Kesehatan dan Keselamatan Kerja dengan Metode Hirarc pada Proyek Pembangunan Sistem Penyediaan Air Baku Bendungan Pengga Kabupaten Lombok Tengah

AbstractThe construction of Pengga Dam bulk water supply system in Central Lombok district has considerable complexity that requires health and safety risk evaluation management, that include part of the project plan and control. This construction consist of several working stage: intake work, jetty work, galvanized pipe connection work, HDPE pipe connection work and pipe bridge construction work. This study uses HIRARC (Hazard Identification Risk Assessment and Risk Control) method consisting of risk identification, risk assessment, and risk control. Risk assessment is explored through field observations and job supervision. Result of the study identifies risks on 7 working stages in which there are any identified potential hazards with multi-levels of risk, in which are low risk, medium risk, up to high risk level. The hazard risk is caused by the absence of occupational safety and health training, inadequate work methods and equipment, the absence of safety signs and complete standardized PPE, also the absence of supervision carried out by the job executor. Risk control should be undertaken in the form of administrating Standard Operating Procedure (SOP) and appropriate use of PPE when carrying out job activities and when in site. Keywords: Hazard Identification Risk Assessment and Risk Control, Bulk Water

A stochastic, daily time-step model for conjunctive water use at local authority level

South Africa has a broadly developed water resource infrastructure, based mainly on surface water, localised groundwater, and limited desalination. The Department of Water and Sanitation projects that increasing requirements will exceed the capacity of the country's bulk water supply systems by 2025. To mitigate water scarcity at a local authority level, more conjunctive water use solutions need to be investigated. A Microsoft Excel 2016 model, estimating supply capacity on a daily basis, was developed for local authorities to better manage their water supply systems. The model utilises synthetically generated stochastic streamflow sequences, based on historical data. Monthly streamflow is disaggregated into daily streamflow and a rainfall-runoff relationship is established to produce synthetic rainfall sequences. Groundwater is modelled using an approach similar to the Aquifer Firm Yield Model. Recharge percentages (rainfall data) are obtained from the Groundwater Resource Assessment Phase 2 project. The Cooper-Jacob model evaluates borehole drawdowns and their effect on surrounding boreholes. Desalination and water reclamation are modelled as one source. The model evaluates and compares the historical, as well as stochastic available yield of a conjunctive use water supply system, for different operational scenarios. The water supply system of Stellenbosch was used as a case study to illustrate the model's functionality.

Public perception of water re-use: building trust in alternative water sources in Malmesbury, South Africa

The recent drought in the Western Cape Province in South Africa has been marked as the worst since 1904. The drought impacted severely on the availability of bulk water supply in many parts of the Western Cape Province, particularly the Cape Town Metro and surrounding districts. In order to alleviate water scarcity, wastewater recycling (water reuse) has been identified to have the potential to augment water supplies in the province. This paper argues that although water recycling has the potential to contribute towards alleviating water scarcity, studies have shown that public perceptions greatly influence the outcome of any water recycling scheme. The study collected data using face-to-face interviews, focus group discussions, and the application of the Story with a Gap participatory exercise. One of the key findings is that residents have to trust the municipal competencies and systems, and this can be achieved through meaningful engagement between the municipality and residents. We argue that rolling out a water reuse scheme by starting with affluent areas increases the likelihood of acceptance among low-income communities.

Policymakers, Consider Reducing Reliability

In this study, the physical and economic impacts of four policy measures (crop diversification, improved watershed development, canal lining and reducing the level of reliability) all designed to improve bulk water supply, are assessed in a case study of the Musi catchment of India. The aim is to compare the impacts these policy measures have on the amount of bulk water supplied and the net economic returns across a complex multi-nodal catchment. It is argued that because it is policymakers who make decisions regarding these measures, an assessment of the private benefits to a subset of users would not be adequate. Rather, the society wide costs and benefits need to be considered. Using a hydroeconomic model of the catchment it was found that reducing the level of reliability was the most beneficial outcome from both a physical and economic perspective. The other three measures were found to have some adverse impacts on regions not directly affected by the measure.

Framework development for the evaluation of conduit hydropower within water distribution systems: A South African case study

The universal lack of access to available water infrastructure data restricts the quantification of hydropower potential and thus the identification of new potential sites. Furthermore, limited research on methods to alleviate the problem associated with hydropower evaluation using limited data exists. To address this deficit, a generic framework was developed to quantify the potential and to identify conduit hydropower sites in bulk water supply systems when limited data poses a challenge. This paper describes the development of the first generic method of evaluating hydropower potential in water infrastructure and provides an example of implementation to verify/validate the range of recommended assumptions using a South African case study. The developed conduit hydropower framework was applied to five case studies to estimate the potential available for three scenarios with different levels of data availability. The analyses showed that on average the variance between the actual potential and the estimated potential available using the developed framework ranges between 6% and 18%. The newly-developed conduit hydropower framework can thus be used to identify hydropower potential in water distribution systems.

Assessing water conditions for Heleophryne rosei tadpoles and the conservation relevance

The Table Mountain Ghost Frog (Heleophryne rosei) is endemic to the Table Mountain massif and is Critically Endangered. Other than clear, clean perennial stream flow, the optimal aquatic conditions required by their larvae are unknown. Dissolved oxygen, temperature, pH, electro-conductivity, aspect and permanence of flow are the independent variables measured seasonally at two sampling altitudes at 12 rivers of the massif. Using a logistic regression model we found that a permanence of water flow and lower water temperature were significant predictors of tadpole presence. Streams with mean summer temperature above 17.2 °C, at 300 m – 400 m above sea level, do not have tadpoles. Summer and autumn abstraction should be avoided, while a summer water temperature above an average of 17.2 °C is a threshold of potential concern for management authorities responsible for biodiversity conservation, threat mitigation efforts, and bulk-water supply and abstraction.Conservation implications: The Environmental Water Reserve has not been determined for streams of Table Mountain. The requirements of the Critically Endangered Table Mountain Ghost Frog (Heleophryne rosei) can be adopted as the minimum conditions to support this species and associated communities. Perennial flow, an average January water temperature of 17.2 °C or lower.

A Fuzzy-Based Evaluation of Financial Risks in Build–Own–Operate–Transfer Water Supply Projects

AbstractThe build–own–operate–transfer (BOOT) scheme is widely used for the provision of new bulk water supply. However, this scheme is complex and carries significant financial risks because of th...

A holistic approach to water supply network operation – using desalination to improve cost efficiency

Seqwater is one of Australia's largest water businesses, with one of the most geographically spread and diverse asset bases. This includes 37 water treatment plants (WTPs), more than 600 km of bulk water supply pipeline, and the Gold Coast Desalination Plant (GCDP) constructed as part of the South East Queensland Millennium Drought response. The production of desalinated water has a greater unit-volumetric cost than the treatment of surface water due to high production energy costs. This paper presents the holistic approach adopted by Seqwater to find a solution for supply contingency while undertaking necessary upgrades and maintenance at the Mudgeeraba WTP. Through a process of network modelling, system risk mapping and financial analysis, it was demonstrated that operating the GCDP for 18 days would provide the best value solution due to the operating costs being offset by bulk supply network operational efficiency improvements.

The potential vulnerability of the Namib and Nama Aquifers due to low recharge levels in the area surrounding the Naukluft Mountains, SW Namibia

The Naukluft Mountains in the Namib Desert are a high rainfall-high discharge area. It sees increased stream-, spring-flow as well as waterfalls during the rainy season. The mountains are a major resource for additional recharge to the Namib and Nama aquifers that are adjacent to the mountains. This paper aimed to highlight the potential vulnerability of the aquifers that surround the Naukluft Mountain area; if the strategic importance of the Naukluft Karst Aquifer (NKA) for bulk water supply becomes necessary. Chloride Mass Balance Method (CMBM) was applied to estimate rainfall available for recharge as well as actual recharge thereof. This was applied using chloride concentration in precipitation, borehole and spring samples collected from the study area. Groundwater flow patterns were mapped from hydraulic head values. A 2D digital elevation model was developed using Arc-GIS. Results highlighted the influence of the NKA on regional groundwater flow. This paper found that groundwater flow was controlled by structural dip and elevation. Groundwater was observed to flow predominantly from the NKA to the south west towards the Namib Aquifer in two distinct flow patterns that separate at the center of the NKA. A distinct groundwater divide was defined between the two flow patterns. A minor flow pattern from the northern parts of the NKA to the north east towards the Nama Aquifer was validated. Due to the substantial water losses, the NKA is not a typical karst aquifer. While the project area receives an average rainfall of 170.36 mm/a, it was estimated that 1–14.24% (maximum 24.43 mm/a) rainfall was available for recharge to the NKA. Actual recharge to the NKA was estimated to be less than 1–18.21% (maximum 4.45 mm/a) reflecting the vast losses incurred by the NKA via discharge. This paper concluded that groundwater resources of the NKA were potentially finite. The possibility of developing the aquifer for bulk water supply would therefore drastically lower recharge to surrounding aquifers that sustain local populations because all received rainfall will be utilized to maximise recharge to the NKA instead of surrounding aquifers.

Examining the potential for energy-positive bulk-water infrastructure to provide long-term urban water security: A systems approach

Urban centres are increasingly requiring more water than existing groundwater and surface water sources can supply. Water authorities must consider energy intensive supply alternatives such as recycling and desalination, leading to a water-energy-climate conundrum. In this study, a systems perspective of the water-energy-climate nexus is applied to South-East Queensland (SEQ), Australia. Under a changing climate, SEQ is predicted to experience reduced reservoir inflows and increased evaporation rates, which will consequently lead to reduced water availability. To exacerbate this issue, anticipated high population growth in SEQ will increase water demand, putting even more stress on the traditional water supply sources. Clearly, there is a strong incentive to pursue solutions that increase water security without contributing to anthropogenic climate change. Using a system dynamics model, the water balance of the bulk water supply system is evaluated over a 100-year life cycle. The outputs of the model are used to investigate potential management and infrastructure options available to SEQ for adapting to increased water scarcity. The historical rainfall patterns of SEQ requires significant contingency to be built into surface water capacity in order to mitigate low rainfall years, and provide adequate water security. In contrast, reverse osmosis (RO) desalination plants do not require this excess capacity because they are rain-independent. However, RO has high energy consumption and associated greenhouse gas emissions when operating and their potential long periods of redundancy due to periods of sufficient surface water supplies remain unresolved issues. The model demonstrates that dual purpose pressure retarded osmosis desalination plants offer a potential solution, by providing water security at a lower cost than surface water reservoir augmentation, while offsetting energy use through renewable energy generation when RO plants would otherwise be sitting idle. Potentially this technology represents a future sustainable solution to overcome water security concerns.

Health Hazards Associated with Consumption of Roof-Collected Rainwater in Urban Areas in Emergency Situations.

The greater Wellington region, New Zealand, is highly vulnerable to large earthquakes because it is cut by active faults. Bulk water supply pipelines cross the Wellington Fault at several different locations, and there is considerable concern about severe disruption of the provision of reticulated water supplies to households and businesses in the aftermath of a large earthquake. A number of policy initiatives have been launched encouraging householders to install rainwater tanks to increase post-disaster resilience. However, little attention has been paid to potential health hazards associated with consumption of these supplies. To assess health hazards for householders in emergency situations, six 200-litre emergency water tanks were installed at properties across the Wellington region, with five tanks being allowed to fill with roof-collected rainwater and one tank being filled with municipal tapwater as a control. Such tanks are predominantly set aside for water storage and, once filled, feature limited drawdown and recharge. Sampling from these tanks was carried out fortnightly for one year, and samples were analysed for E. coli, pH, conductivity, a range of major and trace elements, and organic compounds, enabling an assessment of the evolution of water chemistry in water storage tanks over time. Key findings were that the overall rate of E. coli detections in the rain-fed tanks was 17.7%, which is low in relation to other studies. We propose that low incidences of may be due to biocidal effects of high zinc concentrations in tanks, originating from unpainted galvanised steel roof cladding. Lead concentrations were high compared to other studies, with 69% of rain-fed tank samples exceeding the World Health Organisation’s health-based guideline of 0.01 mg/L. Further work is required to determine risks of short-term consumption of this water in emergency situations.

A systemic framework and analysis of urban water energy

Energy impacts of urban water systems are substantial, but not typically analysed systemically. We develop a new system boundary framework including a utility, the ‘bulk water supply authority’ (SB1); the ‘urban water system’ including water use (SB2); and the ‘regional water system’ (SB3). We use the framework to review existing models and show that most address only one boundary. We apply the framework to quantify thermal equivalents of water-related energy in SB1 and SB2, and identify that over 96% of water-related energy in South East Queensland (SEQ) is outside SB1 and within SB2. Consideration of energy influenced by water use is paramount to systemic energy efficiency and optimisation in the urban water system. Clear articulation of system boundaries will improve modelling and management of the energy impact of urban water. Systemic modelling will help decision makers answer increasingly integrated and cross-system and sector questions regarding water and energy interactions.

Robust optimization to secure urban bulk water supply against extreme drought and uncertain climate change

Urban bulk water systems supply water with high reliability and, in the event of extreme drought, must avoid catastrophic economic and social collapse. In view of the deep uncertainty about future climate change, it is vital that robust solutions be found that secure urban bulk water systems against extreme drought. To tackle this challenge an approach was developed integrating: 1) a stochastic model of multi-site streamflow conditioned on future climate change scenarios; 2) Monte Carlo simulation of the urban bulk water system incorporated into a robust optimization framework and solved using a multi-objective evolutionary algorithm; and 3) a comprehensive decision space including operating rules, investment in new sources and source substitution and a drought contingency plan with multiple actions with increasingly severe economic and social impact. A case study demonstrated the feasibility of this approach for a complex urban bulk water supply system. The primary objective was to minimize the expected present worth cost arising from infrastructure investment, system operation and the social cost of “normal” and emergency restrictions. By introducing a second objective which minimizes either the difference in present worth cost between the driest and wettest future climate change scenarios or the present worth cost for driest climate scenario, the trade-off between efficiency and robustness was identified. The results show that a significant change in investment and operating strategy can occur when the decision maker expresses a stronger preference for robustness and that this depends on the adopted robustness measure. Moreover, solutions are not only impacted by the degree of uncertainty about future climate change but also by the stress imposed on the system and the range of available options.

Long-term water supply planning in an Australian coastal city: Dams or desalination?

Water resource managers and planners are continually involved in defining and evaluating alternative policies to better meet changing water supply conditions and the expectations of society. To undertake such long-term water supply planning, this study developed a novel integrated system dynamics model to combine economic, social and scientific variables and considerations within the planning horizon. Extensive sensitivity analysis for these variables was considered in this long term water resource planning process. The analysis suggests that over a longer time horizon, desalination provides a more viable, cost effective and secure bulk water supply alternative when compared to building large rain-dependent dams.

Drought and Desalination: Melbourne water supply and development choices in the twenty-first century

Sharply reduced catchment inflows across Australia around the end of the twentieth century led to a sequence of water restrictions followed, as the drought persisted, by approximately $10 billion of investments in desalination plants near Perth, Adelaide, Melbourne, Sydney and Brisbane. This Deakin University project jointly with Griffith University, for the National Centre of Excellence in Desalination (NCEDA), follows these new investments. We ask how best to manage bulk water supply and retail supply given the facts and fears of uncertain rainfall, modelled over a 100 year simulation period. We use Monte Carlo style studies aiming to capture the new tensions and trade-offs regarding uncertain climate, rainfall and water supply. There are presently no comprehensive life-cycle approaches to model city water balances that incorporate economic feedbacks, such as tariff adjustment, which can in turn create a financing capacity for such investment responses to low catchment levels, models that could provide significant policy implications for water planners. This project addresses the gap, and presents excerpts from a system dynamics model that augments the usual water utility representation of the physical linkages and water grids. We add inter-connected feedback loops in tariff structures, demand levels and financing capacity. Tariffs are reset in association with drought and the modelling of responses both in terms of reduced consumption and increased revenue to the utility, depending on the elasticities of demand responses to higher tariffs, both short and long term, while also allowing effects from any transitional restrictions. Before reporting on parts of the simulations applied to Melbourne, this paper will first review the general issues surrounding whether desalination is or can be a “game changer” for economic development that hinges on secure water supply. We then explore options in bulk water supply management when desalination augments the choices, including catchments, dams, recycling, pipelines from rivers and savings in irrigation. Finally, the paper addresses the intriguing and important question of the value and cost of providing water for environmental uses.

Influence of site-specific parameters on environmental impacts of desalination

Many metropolitan areas have a high dependency on Seawater Reverse Osmosis (SWRO) desalination plants for bulk water supply. Location and scale decisions are important for SWRO desalination plants owing to the significant environmental costs associated with long distance water pumping. The aim of this study is to introduce a Geographical Information System (GIS)-based method to assist such site-specific decisions. The method has 3 stages. Stage 1 uses GIS to identify feasible plant locations and water demand areas. Stage 2 develops a range of scenarios that balance plant size and number with water demand. In stage 3, the preferred scenario is selected based on environmental life cycle assessment. The method’s applicability was tested using data for the northern corridor of Perth, Western Australia (WA). Spatial water demand and suitable vacant land for accommodating SWRO plants in the case study are obtained in Stage 1. Based on these spatial data, two water planning options are designed in order to supply desalinated water to the demand area. The first option consists of a large SWRO desalination plant and its connected trunk main which supplies water into the demand centrally (centralized scenario). Second option consists of five medium-sized SWRO desalination plants integrated within the demand area (distributed scenario). The best scenario for environmental performance was found to be the distributed scenario which has 18% less GHG emission compared to centralized scenario. This method is adaptable to other case studies for identifying optimal SWRO plant sizes and locations based on environmental criteria.

Speeding up stochastic analysis of bulk water supply systems using a compression heuristic

It is possible to analyse the reliability of municipal storage tanks through stochastic analysis, in which the user demand, fire water demand and pipe failures are simulated using Monte Carlo analysis. While this technique could in principle be used to find the optimal size of a municipal storage tank, in practice the high computational cost of stochastic analyses made this impractical. The purpose of this study was to develop a compression heuristic technique to speed up the stochastic analysis simulations. The compression heuristic uses a pre-run to characterise the failure behaviour of a tank under demand-only conditions, and the stochastic simulations are then only run for periods in which fire demand or pipe failures affect the tank. The compression heuristic method was found to be accurate to within 5% of the full stochastic analysis method. The compression heuristic was also found to be faster than the full stochastic method when more than 27 systems were analysed, and thus allowed genetic algorithm optimisation to be practical by reducing the optimisation simulation time by 75%.Keywords: stochastic analysis; Monte Carlo; optimisation; genetic algorithm; reliability