Water Demand Patterns Research Articles

Discussion of “Effective Approach for Solving Battle of Water Calibration Network Problem” by Zheng Yi Wu and Thomas M. Walski

Discussion of “Effective Approach for Solving Battle of Water Calibration Network Problem” by Zheng Yi Wu and Thomas M. Walski

Non-residential water demand model validated with extensive measurements and surveys

Abstract. Existing Dutch guidelines for the design of the drinking water and hot water system of non-residential buildings are based on outdated assumptions on peak water demand or on unfounded assumptions on hot water demand. They generally overestimate peak demand values required for the design of an efficient and reliable water system. Recently, a procedure was developed based on the end-use model SIMDEUM to derive design-demand-equations for peak demand values of both cold and hot water during various time steps for several types and sizes of non-residential buildings, viz. offices, hotels and nursing homes. In this paper, the design-demand-equations are validated with measurements of cold and hot water patterns on a per second base and with surveys. The good correlation between the simulated water demand patterns and the measured patterns indicates that the basis of the design-demand-equations, the SIMDEUM simulated standardised buildings, is solid. Surveys were held to investigate whether the construction of the standardised buildings based on the dominant variable corresponds with practice. Surveys show that it is difficult to find relationships to equip the standardised buildings with users and appliances. However, the validation proves that with a proper estimation of the number of users and appliances in only the dominant functional room of the standardised buildings, SIMDEUM renders a realistic cold and hot water diurnal demand pattern. Furthermore, the new design-demand-equations based on these standardised buildings give a better prediction of the measured peak values for cold water flow than the existing guidelines. Moreover, the new design-demand-equations can predict hot water use well. In this paper it is illustrated that the new design-demand-equations lead to reliable and improved designs of building installations and water heater capacity, resulting in more hygienic and economical installations.

Estimation of regional irrigation water requirement and water supply risk in the arid region of Northwestern China 1989–2010

Water use in agricultural sector shares more than 90% of the total water withdrawal in the arid region of Northwestern China (hereafter, ARNWC). Irrigation water demand is therefore essential to the water resources allocation to economy and natural ecosystems in the highly water deficit region. In this study, we analyzed the spatial and temporal variations of irrigation water demand as well as crop water requirement by combining the modified Penman–Monteith equation recommended by FAO and GIS technology. Crop and irrigation water requirements for 5 main crops, including wheat, corn, cotton, oilseed and sugar beet, from 1989 to 2010 were calculated and the spatio-temporal variations were analyzed. The results suggested that the demand of irrigation water in the ARNWC showed increasing trend during the past two decades, which mainly caused by fast increase in cotton cultivation areas, because irrigation water requirement for cotton was much larger than the other crops. The changes in cotton growing area significantly affected the spatial pattern of water demand. A total of 44.2 billion m3 water was withdrawn for irrigation in year 2010. Larger amount of water was consumed for crops in Northern Xinjiang and Tarim River Basin than Qilian-Hexi region. Irrigation water requirement reaches its maximum in July and August. It is revealed that the critical period for water supply is during April and May through comparing the monthly irrigation water requirement with water availability, i.e. river discharge. Even though the annual water resources are much larger than the requirement, but for some basins, there is severe physical water shortage during the critical water use period in April and May. The water resource supply is expected to be facing more difficulties in future.

An evaluation of the theoretical potential and practical opportunity for using recycled greywater for domestic purposes in Ghana

Abstract Assessments concerning the effects of climate change, water resource availability and water deprivation in West Africa have not frequently considered the positive contribution to be derived from collecting and reusing water for domestic purposes. Where the originating water is taken from a clean water source and has been used the first time for washing or bathing, this water is commonly called “greywater”. Greywater is a prolific resource that is generated wherever people live. Treated greywater can be used for domestic cleaning, for flushing toilets where appropriate, for washing cars, sometimes for watering kitchen gardens, and for clothes washing prior to rinsing. Therefore, a large theoretical potential exists to increase total water resource availability if greywater were to be widely reused. Locally treated greywater reduces the distribution network requirement, lower construction effort and cost and, wherever possible, minimising the associated carbon footprint. Such locally treated greywater offers significant practical opportunities for increasing the total available water resources at a local level. The reuse of treated greywater is one important action that will help to mitigate the reducing availability of clean water supplies in some areas, and the expected mitigation required in future aligns well with WHO/UNICEF (2012) aspirations. The evaluation of potential opportunities for prioritising greywater systems to support water reuse takes into account the availability of water resources, water use indicators and published estimates in order to understand typical patterns of water demand. The approach supports knowledge acquisition regarding local conditions for enabling capacity building for greywater reuse, the understanding of systems that are most likely to encourage greywater reuse, and practices and future actions to stimulate greywater infrastructure planning, design and implementation. Although reuse might be considered to increase the uncertainty of achieving a specified quality of the water supply, robust methods and technologies are available for local treatment. Resource strategies for greywater reuse have the potential to consistently improve water efficiency and availability in water impoverished and water stressed regions of Ghana and West Africa. Untreated greywater is referred to as “greywater”; treated greywater is referred to as “treated greywater” in this paper.

Spatial Distribution of Tree Species Governs the Spatio-Temporal Interaction of Leaf Area Index and Soil Moisture across a Forested Landscape

Quantifying coupled spatio-temporal dynamics of phenology and hydrology and understanding underlying processes is a fundamental challenge in ecohydrology. While variation in phenology and factors influencing it have attracted the attention of ecologists for a long time, the influence of biodiversity on coupled dynamics of phenology and hydrology across a landscape is largely untested. We measured leaf area index (L) and volumetric soil water content (θ) on a co-located spatial grid to characterize forest phenology and hydrology across a forested catchment in central Pennsylvania during 2010. We used hierarchical Bayesian modeling to quantify spatio-temporal patterns of L and θ. Our results suggest that the spatial distribution of tree species across the landscape created unique spatio-temporal patterns of L, which created patterns of water demand reflected in variable soil moisture across space and time. We found a lag of about 11 days between increase in L and decline in θ. Vegetation and soil moisture become increasingly homogenized and coupled from leaf-onset to maturity but heterogeneous and uncoupled from leaf maturity to senescence. Our results provide insight into spatio-temporal coupling between biodiversity and soil hydrology that is useful to enhance ecohydrological modeling in humid temperate forests.

Evaluation of plumbed rainwater tanks in households for sustainable water resource management: a real-time monitoring study

In recent years, there has been a significant emphasis placed on achieving reductions in urban residential water demand through the application of alternative water resources on various housing development scales based on a “fit-for-purpose” concept. One such resource is rainwater that could be used in various non-potable applications at household level in urban areas. Savings in mains water achieved through the inclusion of rainwater as a source for residential use are plausible; however, analyses on quantifying the actual reduction in mains water demand are still at an early stage to incorporate into strategic planning for urban water supply. This paper highlights the real-time monitoring outcomes of 20 detached households with plumbed rainwater tanks in an attempt to assess their volumetric reliabilities, diurnal water demand patterns and water energy nexus. The rainwater usage (or mains water saving) was validated and assessed using 12 months monitoring data and an average yearly rainwater usage of 40 kl/household was found. The volumetric reliability, which is the ratio of the rainwater usage to the total household water demand, was found to be on average 31%. The instantaneous peak water demand was estimated to range between 16 and 93 l/min within the monitored homes, which has a strong implication for the design of household water supply system. Furthermore, the specific energy usage for rainwater supply in the 20 homes was estimated to be 1.52 kWh/kl. This study constitutes important research which provides critical input into strategic urban water planning for sustainable water resource management. The study is focussed on the South East Queensland region of Australia but the methodology developed for the monitoring and assessment of water savings in households with plumbed rainwater tanks will be useful for adoption worldwide by water professionals engaged in alternative water resources planning for urban developments.

Predicting normalised monthly patterns of domestic external water demand using rainfall and temperature data

An Australian national approach is presented to predict monthly patterns of local domestic external water demand from climatic indices of daily rainfall and maximum temperature. The model, which can be rapidly applied to potentially any location in Australia, has been verified by measured monthly external water demand at Adelaide, Bundaberg, Emerald, Fraser Coast, Gold Coast, Mackay, Melbourne, Newcastle, Perth and Toowoomba. The survey data represents demands in periods prior to, during and after the millennium drought of 2001–2005 by discontinuously spanning 25 years from 1985 to 2010. The model avoids local calibration through a national regression of parameters. A demand index is produced that predicts daily proportions of annual demand. Results show that the model is capable of identifying 90% of the spatial and temporal variability in water demand, based on daily index summations by month. This research is useful for reliability estimates of intermittent water supplies, such as rainwater harvesting.

Principal Factor Analysis for Forecasting Diurnal Water-Demand Pattern Using Combined Rough-Set and Fuzzy-Clustering Technique

AbstractThe true principal factors for the diurnal water-demand pattern of urban water are often difficult to identify using traditional rough-set algorithms because the demand pattern is usually affected by many factors that are uncertain and hard to quantify. An improved attribute-reduction algorithm based on the cumulative weighting coefficient was proposed to solve this problem. The weighting coefficient was determined by the result of the variable precision rough-set algorithm. To discuss the consecutive curves with mathematical tools, an improved fuzzy c-mean (FCM) algorithm was proposed to discretize the diurnal water-demand pattern spatially. The proposed algorithms were then used to analyze the principal factors of the diurnal water-demand pattern in the city of Hangzhou, China. The results show that the improved attribute-reduction algorithm is capable of distinguishing the false attribute from the dynamic reduction sets, and the fuzzy c-mean algorithm is an effective and feasible method of solv...

Impact of different water price levels on irrigated agriculture in Northern Jordan Valley

A linear programming model was developed to assess the impact of different water prices on cultivated areas, irrigation water demand, net income and optimal cropping pattern in the Northern Jordan Valley (NJV). The results reveal that the price for irrigation water does not reflect any elasticity in the range of water prices between 0.01 and 0.06 JD/M3 indicating constant real economic water price of 0.06 JD/M3. The change in cultivated areas as well as water demand (reduction) starts at water price 0.07 JD/M3. The expected reductions under optimal cropping patterns are 5%, 24%, and 60% for cultivated area and 4.7%, 18.9%, and 31% for water demand with water prices at 0.07, 0.1, and 0.16 JD/M3, respectively. Significant reductions in net incomes are resulted with increasing water prices over current average water price of 0.025 JD/M3. The expected reductions in net incomes are 33.6%, 53.8%, and 81.4% at water prices 0.07, 0.1, and 0.16 JD/M3, respectively. This result reflects the low land profitability as a result of low land productivity and/or low farm gate sale prices for most crops grown in NJV. The study also shows the inconsistency in quantity of water supplied and water demanded, leading to unbalanced water budget on monthly level and inconsequence, a noticeable waste in the quantity of available water during winter months, although there is a net surplus of water over the year. While the findings of this research reveal that a water price in the range of 0.07–0.1 JD/M3 does not significantly influence the farmers' socio-economic parameters in the NJV, it may help reach the stated goal of saving water especially when monthly distributions of irrigation water are based on real crops water demands and actual cropping patterns.

Environmentally friendly hybrid solutions to improve the energy and hydraulic efficiency in water supply systems

Electricity is needed to extract, treat and convey water. Water service providers recognize that electricity costs constitute one of the biggest operational costs of Water Supply Systems (WSS). The practice of water supply requires new energy management strategies and solutions which need to improve WSS energy and hydraulic efficiency and to be innovative, cost-effective and environmentally friendly. Three management practices and solutions for WSS are presented and analyzed in this paper. The first solution proposes the installation of a water turbine in gravity pipes for pressure control and for electricity production. The second solution is the optimization of pump operational schedules according to electricity tariffs and water demand patterns. The third solution focuses on the coupling of a renewable energy source capturing device (a wind turbine) to a water supply pumping station in a hybrid configuration. The studied water system, typical for Water District Metering Areas (DMAs), represents a conventional WSS, which consists of pump and gravity branches. The main findings suggest that water turbines can be used to take advantage of the excess and otherwise unutilized available hydraulic energy in piping systems and to convert it into electricity. The optimization of WSS pump operational schedules and the renewable hybrid electricity producing solution can both minimize operational costs and electricity consumption for water pumping. The use of a wind turbine results in electricity production from a renewable energy source, which minimizes the reliance on electricity produced from fossil fuels. The result is minimized CO 2 emissions depending on the emissions factor of the electricity transmission grid and the generated electricity can be used locally or fed to the national electricity transmission grid.

Water scarcity and climate change adaptation for Yemen's vulnerable communities

Yemen faces formidable freshwater management challenges. Devising policies for sustainable use and allocation of limited water resources is made difficult by substantial population growth, degrading environmental quality and uncertainty regarding possible changes in water availability due to climate change. We use the Water Resources Evaluation and Planning software to evaluate water needs and scarcity for three case study areas in Yemen representing different ecological conditions (Sana'a, Sadah, and Aden City) under a range of scenarios that include potential climate change and adaptation strategies. These management strategies, identified by stakeholder processes, have the potential to reduce vulnerability and build resilience. The modelled results suggest that current and predicted patterns of water consumption will soon fully deplete available supplies, and are a bigger driver of vulnerability than potential climate change for the region. In the absence of new strategies to bring into balance water supply and demand patterns, results for all three case studies suggest the pressing water crisis will only worsen. Timely interventions, designed to build resilience to scarcity, are urgently needed.

A bottom-up approach of stochastic demand allocation in a hydraulic network model: a sensitivity study of model parameters

An “all pipes” hydraulic model of a drinking water distribution system was constructed with a bottom-up approach of demand allocation. This means that each individual home is represented by one demand node with its own stochastic water demand pattern. These water demand patterns were constructed with the end-use model SIMDEUM. A sensitivity test with respect to the resulting residence times was performed for several model parameters: time step, spatial aggregation, spatial correlation, demand pattern and number of simulation runs. The bottom-up approach of demand allocation was also compared to the conventional top-down approach, i.e. a single demand multiplier pattern is allocated to all demand nodes with the base demand to account for the average water demand on that node. The models were compared to measured flows and residence times in a small network. The study showed that the bottom-up approach leads to realistic water demand patterns and residence times, without the need for any flow measurements. The stochastic approach of hydraulic modelling, with a 15 minute time step, some spatial aggregation and 10 simulation runs, gives insight into the variability of residence times as an added feature beyond the conventional way of modelling.

Weather, Climate, and Environmental Water Transactions

Abstract Obtaining water for environmental purposes, such as habitat restoration or water quality improvements, has become an important objective in many parts of the world. Such water acquisitions are likely to become more challenging as regional water demand and supply patterns are altered by climate change. In regions where water supplies are already fully claimed, voluntary negotiated transactions have become a key means to obtain water for the environment. The cost of acquiring water in such transactions is hypothesized to vary with regional weather and climate conditions due to both the actual effects of temperature and precipitation on water supply and demand and the perceptions water users may hold about these effects. This article develops econometric models to examine the effect of temperature and precipitation on water lease prices in four U.S. states located in the desert southwest. Water leases for environmental and nonenvironmental purposes are contrasted to understand the differing nature of these lease markets and the role of weather and climate variables. The authors’ analysis finds that temperature, precipitation, regional income, and population changes are variables that have differing effects in the two lease markets. Overall, analysis of over 20 yr of data shows the need to consider climate and weather factors given the growing importance of water leases as a tool to secure water for the environment.

Crop water use efficiency at multiple scales

Food security is an issue of global concern, which is tightly linked with water supply issues as regional demands for water are dominated by agricultural water use. This special issue of Agricultural Water Management focuses on crop–water use in China, especially in the North China Plain (NCP) and Loess Plateau and surrounding areas, where intensive agriculture (e.g., wheat–maize double cropping) with limited water is practiced to meet the large demand for grains. Such intensive agriculture raises concerns for agricultural sustainability due to limited water supply and effects on water quality, which may be aggravated by projected climate change and its variability across the region and over time. Addressing these issues requires basic understanding of crop–water relationships in water-limited agricultural systems, methods to quantify water demand and actual crop–water use over multiple scales, and strategies to improve water use efficiency (WUE, or water productivity). Advances in crop breeding (selection) and agronomic management, such as irrigation and nutrient management, and tools to assess and improve WUE at multiple scales are addressed for a range of cropping systems in China. Water supplies within a basin (regional scale) must be managed in view of the patterns of water demand in space and time determined by soil and climatic conditions.

Introducing competition into England and Wales water industry – Lessons from UK and EU energy market liberalisation

This paper summarises the experience concerning electricity and natural gas in the UK and the European Union since the 1980s with a view to drawing lessons for potential liberalisation and the introduction of competition into the England and Wales water industry. The paper suggests that the main lesson from energy sector experience is the requirement is to develop upstream competition in the supply of bulk water both to retail supply companies and to large industrial consumers. The pattern of water supply and demand in England and Wales is that there are excess supplies in the North and West and supply shortages in the South and East. In consequence, provided that there is sufficient interconnection capacity within and between regions, there should be major potential gains from trade both in bulk water supplies as well as in trade of abstraction licences. Such trade can offer potentially sizeable environmental benefits in terms of water sustainability as well as in short and long-term efficiency benefits to consumers. The paper concludes with recommendations for some experiments with abstraction licence and bulk water trading, e.g. in the South East of England.

A bottom-up approach of stochastic demand allocation in water quality modelling

Abstract. An "all pipes" hydraulic model of a drinking water distribution system was constructed with two types of demand allocations. One is constructed with the conventional top-down approach, i.e. a demand multiplier pattern from the booster station is allocated to all demand nodes with a correction factor to account for the average water demand on that node. The other is constructed with a bottom-up approach of demand allocation, i.e., each individual home is represented by one demand node with its own stochastic water demand pattern. This was done for a drinking water distribution system of approximately 10 km of mains and serving ca. 1000 homes. The system was tested in a real life situation. The stochastic water demand patterns were constructed with the end-use model SIMDEUM on a per second basis and per individual home. Before applying the demand patterns in a network model, some temporal aggregation was done. The flow entering the test area was measured and a tracer test with sodium chloride was performed to determine travel times. The two models were validated on the total sum of demands and on travel times. The study showed that the bottom-up approach leads to realistic water demand patterns and travel times, without the need for any flow measurements or calibration. In the periphery of the drinking water distribution system it is not possible to calibrate models on pressure, because head losses are too low. The study shows that in the periphery it is also difficult to calibrate on water quality (e.g. with tracer measurements), as a consequence of the high variability between days. The stochastic approach of hydraulic modelling gives insight into the variability of travel times as an added feature beyond the conventional way of modelling.

Exploration of an Efficient Control Rule Set of a Heat Pump Water Heater by Genetic Algorithms

The system most widely employed in existing heat pump water heaters is based on three rules, the parameters of which used to calculate the amount of hot water required are fixed. A method exists to optimize parameters in the three rules; however, this parameter optimization method remains insufficient for many types of heaters since the method does not take demand patterns fully into account. Parameter optimization optimizes a control rule set simply assuming that a storage tank has sufficient capacity for a whole day demand. We propose a new method for generating an control rule set that minimizes running costs based on hot water demand patterns. Our method adopts a new rule format which can control the heaters more flexibly than parameter optimization. The control rule set is explored by Genetic Algorithm (GA) and a computer simulation of the heat pump water heater. To evaluate our method, we explored control rule sets for two types of storage tanks for three actual consumers. Our method generated efficient control rule sets that adapt to changes of hot water demand patterns. Consequently, over 20% of running costs were reduced compared to the control rule set optimized by parameter optimization.

The energy-efficiency benefits of pump-scheduling optimization for potable water supplies

Water utilities across the developed world have been installing and operating telemetry and SCADA (supervisory control and data acquisition) facilities for at least three decades. They have amassed substantial quantities of historical operational data held in databases called data warehouses. Significant interest exists for extracting the underlying value from this data to support decision making and performance improvement. The water industry uses approximately 3% of total electricity production in developed countries such as the United Kingdom and the United States. Up to 90% of this electrical energy is consumed by pumps. Small improvements in pump efficiency will yield significant reductions in energy consumption with consequential reductions of carbon emissions to the atmosphere. Technologies to initially select a pump to match the expected performance requirements and then maintain optimal performance through periodic refurbishment are well established. Dynamically optimizing the scheduling of pump operation to improve efficiency under changing diurnal and seasonal water demand patterns is far more complex. This paper summarizes 20 years of progress in the development of pump efficiency improvement techniques and focuses on real-time dynamic optimization technologies and data-mining techniques to improve energy efficiency. Case study results from an automated real-time commercial pump-scheduling system, Aquadapt™, are presented.

Simulating Residential Water Demand with a Stochastic End-Use Model

A water demand end-use model was developed to predict water demand patterns with a small time scale (1 s) and small spatial scale (residence level). The end-use model is based on statistical inform...

Water Rationing Model for Consequence Minimization of Water Infrastructure Destruction

This paper describes a model developed for optimizing water supply plans for water customers when a water network is partially operational due to the destruction of water networks by malicious attacks or any catastrophic events. The model uses the information regarding the priority of water customers in emergency situations, their functional sensitivities to water supply, and the dynamic nature of water demand patterns. The solutions generated from the model are water rationing plans which can guarantee at least a short-term water supply to water customers during any 24-h period. A genetic algorithm based program linked with a hydraulic solver (EPANET 2.0) is developed to find optimal water rationing plans. A case study indicates that the proposed model can successfully generate water rationing plans to reduce the consequences while meeting hydraulic constraints in water networks. The model developed in this study is also applicable to extreme water supply shortage situations due to severe drought or nonintentional incidents such as major pump failures and main breaks.