Methodology for Detecting Critical Points in Pressurized Irrigation Networks with Multiple Water Supply Points

The modernization processes of hydraulic infrastructures from old open channels to pressurized networks have increased water use efficiency along with a dramatic increase of energy consumptions. The significant energy requirements associated with the increment of the energy tariffs for irrigation involve higher production costs for farmers. Therefore, strategies to reduce energy consumption in irrigation districts are strongly demanded. Methodologies based on sectoring and critical points control have been applied to branched networks with a single water supply point, obtaining significant energy savings. In this work, a new critical point control methodology for networks with multiple sources has been developed: the WEPCM algorithm, which uses the NSGA-II multi-objective evolutionary algorithm to find the lowest energy consumption operation rule of a set of pumping stations connected to an irrigation network that satisfies the pressure requirements, when the critical points are successively disabled. WECPM has been applied to a real irrigation district in Southern Spain. The obtained results were compared with those achieved by the WEBSOM algorithm, developed for sectoring multiple source networks. The control of critical points by the replacement of two pipes and the installation of four booster pumps provided annual energy savings of 36 % compared to the current network operation. Moreover, the control of critical points was more effective than sectoring, obtaining an additional annual energy saving of 10 %.     

Detecting Critical Points in On-Demand Irrigation Pressurized Networks – A New Methodology

In many pressurized irrigation water distribution networks, rising energy costs are having a significant impact on system performance, environmental impact and the profitability of agribusinesses and farms dependant on water supplies for irrigated production. In this study, a new methodology is proposed for analysing the location of critical control points (hydrants) to reduce energy consumption. The methodology is developed and applied using two irrigation districts located in Southern Spain (Fuente Palmera and El Villar). The new approaches provide a framework for comparing different energy saving strategies, including improved critical point management and network sectoring. The results show that potential energy savings of around 10% and 30% are possible in each district when the theoretical irrigation requirements are modeled. However these savings reduce to 5% and 12% when the local farmers’ practices of deficit irrigation are incorporated. These results are compared to those obtained for networks sectoring in the same irrigation networks in a previous work. The study confirms that that a sectoring approach works best for reducing the energy costs associated with meeting actual irrigation water demands in irrigation districts where energy consumption is a limiting factor on production.     

Incorporating the Irrigation Demand Simultaneity in the Optimal Operation of Pressurized Networks with Several Water Supply Points

Network sectoring is one of the most effective measures to reduce energy consumption in pressurized irrigation networks. In this work, the previous model focused on the irrigation networks sectoring with several supply points (WEBSOM), which considered the simultaneous operation of all hydrants, has been improved by integrating an analysis of multiple random demand patterns and their effects on variability in hydrant pressure (extended WEBSOM). The extended WEBSOM has implied a multiobjective optimization, followed by a Montecarlo procedure to analyze different flow regimes using quality of service indicators, a novelty for multi-source pressurized irrigation networks. This innovation has involved energy savings ranging from 9 to 15 % with respect to the consideration of the concurrent operation of all hydrants, which rarely occurs in on-farm irrigation systems. These energy savings were associated with maximum values of pressure deficit of 21 and 34 % in the most critical hydrant with a deficit frequency of 27 and 36 % in the peak month. However, smaller and less frequent deficits were achieved in the rest of the months. Thus, substantial energy savings can be obtained in irrigation districts without significant losses in the service quality provided to farmers.     

Optimization of Irrigation Scheduling Using Soil Water Balance and Genetic Algorithms

In arid and semi-arid countries, the use of irrigation is essential to ensure agricultural production. Irrigation water use is expected to increase in the near future due to several factors such as the growing demand of food and biofuel under a probable climate change scenario. For this reason, the improvement of irrigation water use efficiency has been one of the main drivers of the upgrading process of irrigation systems in countries like Spain, where irrigation water use is around 70 % of its total water use. Pressurized networks have replaced the obsolete open-channel distribution systems and on farm irrigation systems have been also upgraded incorporating more efficient water emitters like drippers or sprinklers. Although pressurized networks have significant energy requirements, increasing operational costs. In these circumstances farmers may be unable to afford such expense if their production is devoted to low-value crops. Thus, in this work, a new approach of sustainable management of pressurized irrigation networks has been developed using multiobjective genetic algorithms. The model establishes the optimal sectoring operation during the irrigation season that maximize farmer’s profit and minimize energy cost at the pumping station whilst satisfying water demand of crops at hydrant level taking into account the soil water balance at farm scale. This methodology has been applied to a real irrigation network in Southern Spain. The results show that it is possible to reduce energy cost and improve water use efficiency simultaneously by a comprehensive irrigation management leading, in the studied case, to energy cost savings close to 15 % without significant reduction of crop yield.     

Energy and Hydraulic Performance-Based Management of Large-Scale Pressurized Irrigation Systems

Improving energy and hydraulic performance of large-scale pressurized irrigation is now perceived as a very pressing need, after large budgets have been allocated into systems modernization. This paper tackles this priority area by developing a management oriented multi-step methodology, that integrates different existing models, to sector the system according to the pressure requirements of the hydrants, and to regulate the pumping station for i) a fixed and a variable pressure head control, and for ii) an enhanced performance. When applied to an on-demand system in the Sinistra Ofanto irrigation scheme of Foggia (Italy), this integrated approach showed potential for energy saving under the optimal scenario of 49 %, and noticeable improvement in the system performance in terms of hydrant pressure heads, as compared to the actual conditions. The monetary assessment demonstrates that the achieved energy saving amounts to 23,636 Euros per irrigation season, 45 % among which are due to sectoring.     

Optimal Design of Pressurized Irrigation Networks to Minimize the Operational Cost under Different Management Scenarios

The adoption of measures leading to higher efficiencies in the use of both water and energy in water distribution networks is strongly demanded. The methodology proposed combines a multi-objective approach and a financial analysis to determine de optimal design of pressurized irrigation networks which entails the minimization of both the investment cost and operational cost under three operating scenarios that incorporate energy saving strategies: 1- all hydrants operate simultaneously; 2- hydrants are grouped into sectors and irrigation turns are established; 3- the on-demand operation of the network is assumed. This methodology has been applied in a real irrigation network located in Southern Spain showing that the lowest overall design cost (investment and operational costs) is achieved in scenario 2. The comparison of the selected solutions in the three proposed scenarios with the current network design considering the total fulfillment of irrigation requirements showed that operational cost savings between 65% and 76% could be achieved.     

Water Saving and Energy Reduction through Pressure Management in Urban Water Distribution Networks

Water shortages and climate change are worldwide issues. Reduction in water leakage in distribution networks as well as the associated energy saving and environmental impacts have recently received increased attention by scientists and water industries. Pressure management has been proposed as a cost-effective approach for reduction in water leakage. This study conducted a real-world water pressure regulation experiment to establish the pressure-leakage relationship in a district metering area (DMA) of the water distribution network in Beijing, China. Results showed that flow into the DMA was sensitive to inlet water pressure. A 5.6 m reduction in inlet pressure (from 38.8 m to 33.2 m) led to an 83 % reduction (12.1 l/s) in minimal night flow, which is a good approximator of leakage. These reductions resulted in 62,633 m³ of water saved every year for every km pipe, as well as associated savings of 1.1?×?10⁶ MJ of energy and 68 t of CO₂ equivalent greenhouse gas emissions. The results of this study provide decision makers with advice for reducing leakage in water distribution networks with associated energy and environmental benefits.     

Strategien und Potenziale zur Energieoptimierung bei der Wasserwiederverwendung

The energy and materials derived from treating sewage are becoming increasingly important worldwide and are thus progressively considered resources rather than a disposal problem. This is also apparent in the growing interest in recycling water from municipal wastewater for both non-potable and potable purposes, supplementing the drinking water supply in the latter case. However, the energy consumption of about 0.9–1.8 kWh/m³, required to recycle drinking water, is not insignificant. Due to the lack of national as well as international standardized regulatory specifications for recycled water quality, very different technical solutions for potable water reuse have been deployed worldwide. Therefore, energy-saving measures often can only be applied to internal operational optimizations and the achievable savings are rather limited. Strategies for integrated energy recovery, the increased use of anaerobic biological processes and combined heat and power (CHP) for water recycling are hence very promising. These provide opportunities for internal power provision and therefore options to reduce the specific energy requirements for potable water reuse to well below 1 kWh/m³, despite the necessary treatment processes. However, the greatest potential for energy-efficient water recycling is at the regional planning level. Recycling water is only attractive where local freshwater resources are insufficient or there is a dependency on imported water, and it is the significantly more cost-effective option than the treatment of brackish or sea water.     

The Pros and Cons of Encouraging Shallow Groundwater Use through Controlled Drainage in a Salt-Impacted Irrigation Area

Encouraging shallow groundwater use through water table management or controlled drainage in irrigated areas can relief crop water stress under water shortage condition. But substituting fresh irrigation water with saline groundwater may speed up salinity buildup in the crop root zone, and consequently increase water use for salt leaching. With a proposed analytical model, this paper presents a case study demonstrating the effect of encouraging shallow groundwater use through controlled drainage on salt and water management in a semi-arid irrigation area in northwestern China. Based on the average rainfall condition, the model assumes that salt accumulates in the crop root zone due to irrigation and shallow groundwater use; till the average soil salinity reaches the crop tolerance level, leaching irrigation is performed and the drainage outlet is lowered to discharge the salt-laden leaching water. For the relatively salt tolerant crop–cotton in the study area, the predicted leaching cycle was as long as 751 days using the fresh water (with salinity of 0.5 g/L) irrigation only; it was shortened to 268 days when the water table depth was controlled at 2 m and 23% of the crop water requirement was contributed from the saline groundwater (with salinity of 4.43 g/L). The predicted leaching cycle was 140 days when the water table depth was controlled at 1.5 m and groundwater contribution was 41% of the crop water requirement; it was shortened to 119 days when the water table depth was controlled at 1.2 m and the groundwater contribution was 67% of the crop water requirements. So the benefit from encouraged shallow groundwater use through controlled drainage is obtained at the expense of shortened leaching cycle; but the shallow groundwater use by crops consists of a significant portion of crop water requirements, and the leaching cycle remains long enough to provide a time window for scheduled leaching in the off season of irrigation. Weighing the pros and cons of the encouraged shallow groundwater use may help plan irrigation and drainage practices to achieve higher water use efficiency in saline agricultural areas.     

Urban Sustainability Incentives for Residential Water Conservation: Adoption of Multiple High Efficiency Appliances

Effects of multiple types of water use efficiency appliances on long term water savings and water use trend shifts were analyzed. The study group included senior and low income families in the urban areas of Miami-Dade County, Florida, USA. The participants in the study group experienced continuous and significant water savings within 3 years of the implementation of the water conservation incentives. Water savings were observed at approximately 200 l per household per day, which is about 31 % reduction in household water demand in comparison to the average residential water demand within the County. The water use profile of participants showed noticeable shifts over time in water demand frequency curves toward lower water consumption rates. The cost-saving analysis showed that adoption of multiple water efficiency appliances contributed to the highest annual monetary savings (i.e., high water savings and moderate product costs). Future conservation program planning efforts should take both water savings and product cost into account in order to achieve the greatest benefits.     

Design of Sprinkler Irrigation Subunit of Minimum Cost with Proper Operation. Application at Corn Crop in Spain

MATLAB^? software named PRESUD (Pressurized Subunit Design) was developed to identify the optimum solid set sprinkler irrigation subunit design with a criterion of minimizing the annual water application cost (C_T). This C_T is defined as the cost per cubic meter of water applied to the soil for crop use. In this study, only rectangular subunits are considered, using an iterative method for calculating the lateral and manifold pipelines. The results indicate that water cost (C_w)_, which includes the investment and operation costs for pumping water from the source to the subunit inlet, makes up 75 % of C_T. Another important factor is energy cost, which comprises 14 % of C_T. The remaining variables, such as sprinkler spacing and layout, or application rate (AR_a), have a lower impact on C_T. In cases of use groundwater, the proportion of energy cost in C_W can reach 40 %; thus, energy is an important part of C_T. Results shows that the criterion of limiting the maximum difference in pressure heads in the irrigation subunit (Δh?T, and the use of tools such as PRESUD can help obtain better solutions.     

An Integrated Model to Evaluate Losses in Water Distribution Systems

To evaluate non revenue water (NRW) and losses in water distribution networks a methodology is developed by applying “annual water balance” and “minimum night flow” analyses. In this approach the main NRW components such as leakage from reported and un-reported bursts and background leakage, with real or estimated data, enabling assessment of indices of leakage performance are evaluated. Also, a novel procedure is introduced in this paper that can determine the nodal and pipe leakage by using a hydraulic simulation model. Recognising the pressure dependency of leakage the total consumption is divided into two parts, one pressure dependent and the other independent of local pressure, and the hydraulic behaviour of the network is analyzed. A computer code is developed to evaluate all components of water losses based on the proposed methodology. For better representation of the results and management of the system, the outputs are exported to a GIS model. Using the capabilities of this GIS model, the network map and attribute data are linked and factors affecting network leakage are identified. In addition, the effects of pressure reduction are investigated. The model is illustrated by a real case study. The results show that the suggested model has overcome the shortcomings of the existing methodologies by accounting for the leakage and other NRW components in water distribution networks more realistically.     

Assessment of Potable Water Savings in Office Buildings Considering Embodied Energy

The objective of this article is to assess the potential for potable water savings in office buildings located in Florianópolis, southern Brazil. The embodied energy of four alternatives to reduce potable water demand, i.e., rainwater harvesting, greywater reuse, dual-flush toilets and water-saving taps, was also assessed. The analyses took into account the potable water end-uses for ten buildings. The potential for potable water savings by using rainwater, as well as, the rainwater tank sizing were estimated using computer simulation. As for greywater reuse, it was considered that greywater from lavatory taps could be treated and reused to flush toilets. The potential for potable water savings by using water-saving plumbing fixtures was estimated by considering the replacement of toilets and taps. In order to estimate the embodied energy in the main components, each system was dimensioned and embodied energy indices were applied. The main result is that the potential for potable water savings by using dual-flush toilets ranges from 21.6 % to 57.4 %; by reusing greywater, it ranges from 6.8 % to 38.4 %; by using rainwater, it ranges from 6.1 % to 21.2 %; by using water-saving taps it ranges from 2.7 % to 15.4 %. However, by considering the embodied energy, the average for the ten buildings indicates that dual-flush toilets are the best choice as it is possible to obtain water savings of 5.50 m³/month per GJ of embodied energy, followed, respectively, by water-saving taps, greywater reuse and rainwater usage. The main conclusion is that the assessment of embodied energy should be considered when evaluating potable water savings in buildings as it helps to identify the best alternatives to save more water while causing less environmental impact.     

Simulating system‐wide effects of reducing irrigation withdrawals in a disputed river basin

Stakeholders in river systems often target larger upstream water consumers as an intuitive solution for increasing flows for downstream ecological needs. Within regulated river systems, simplistic panaceas may have unexpected and unintended results at a watershed level. The Apalachicola–Chattahoochee–Flint River Basin is a large watershed in the south‐eastern United States whose management has been the source of conflict for several decades. This paper tests the hypothesis of whether a reduction in consumptive losses to Flint River flows through the large‐scale implementation of water‐saving agricultural irrigation technologies and practices will have a positive effect on downstream ecosystem water requirements in the Apalachicola River. An existing integrated reservoir/reach model was used to explore multiple irrigation water use scenarios. Because of current federal reservoir operating rules in the Chattahoochee River, irrigation decreases in the Flint River do not always directly translate to elevated flows downstream in the Apalachicola River. In drought years, a large percentage of the Flint River water savings is captured as greater storage volume at upstream Chattahoochee reservoirs because of a requirement to supplement downstream flows to a prescribed minimum level. In nondrought years, the majority of irrigation decreases translate to increased flow in the Apalachicola River. Given these simulation results, public policy decisions need to be formulated with regard to what portion of the Flint River water savings from changing irrigation practices in drought years should be allocated to the upstream Chattahoochee storage reservoirs and what portion to supporting downstream environmental and social needs in the Apalachicola watershed.     

Performance Analysis of a Communal Residential Rainwater System for Potable Supply: A Case Study in Brisbane, Australia

Cities in developed countries have increasingly adopted rainwater tanks as an alternative water source over the last 15 years. The rapid uptake of rainwater tanks has been driven by the need to reduce demand for centralised water services that are under pressure to adapt to population growth and climate change impacts. Rainwater tanks are part of integrated urban water management approach that considers the whole water cycle to provide water services on a fit for purpose basis that minimises the impact on the local environment and receiving waters. Rainwater tanks are typically applied at the household scale for non-potable water source uses such as toilet flushing and garden irrigation. However, this paper reports on a communal approach to rainwater harvesting, where the water is treated for potable use. A communal approach to rainwater harvesting can offer benefits, such as: economies of scale for capital costs, reduced land footprint, centralised disinfection and flexibility in matching supply and demand for different households. The analysis showed that the communal approach could provide a reliable potable water source to a small urban development. However, there was an energy penalty associated with this water source compared to centralised systems that could be addressed through more appropriate pump sizing. The outputs from this monitoring and modelling study demonstrated rainwater harvesting can be expanded beyond the current mainstream practices of household systems for non-potable use in certain development contexts. The analysis contained in this paper can be used for the improved planning and design of communal approaches to rainwater harvesting.     

Rehabilitation of Irrigation Distribution Systems: The Case of Jericho City

Efficiency enhancement in irrigation distribution system (IDS) contributes to substantial water savings. This paper aims to present the methodology and lessons learned from efforts to improve efficiency in the irrigation distribution system of Jericho City. This effort presents a new paradigm in water management in water scarce countries, which focuses on both supply and demand management rather than on supply augmentation. Converting the existing irrigation canal system to a pressurized pipe network carries out rehabilitation of IDS in Jericho City. Analysis of the new IDS is performed through computer simulation. Considerations and constraints for sustainable irrigation management are presented.     

Irrigation energy use and related greenhouse gas emissions of maize production in Mexico

Maize is the most important crop grown in Mexico, with more than one-third of total production coming from irrigated fields. We compute irrigation energy use and associated greenhouse gas emissions of different irrigated maize systems in Mexico. Calculations were based on National Agriculture and Forestry Census 2007 microdata, irrigation water requirements estimated from state-level climate data, and energy and emission coefficients from the literature. Weighted average irrigation energy and related emissions are in the range of 1.0–31.6 GJ/ha and 62.0–2,019.9 kg CO₂e/ha, respectively, while country-scale estimates amount to 4.8 PJ and 305.2 Gg CO₂e.     

Joint optimization scheduling for water conservancy projects in complex river networks

In this study, we simulated water flow in a water conservancy project consisting of various hydraulic structures, such as sluices, pumping stations, hydropower stations, ship locks, and culverts, and developed a multi-period and multi-variable joint optimization scheduling model for flood control, drainage, and irrigation. In this model, the number of sluice holes, pump units, and hydropower station units to be opened were used as decision variables, and different optimization objectives and constraints were considered. This model was solved with improved genetic algorithms and verified using the Huaian Water Conservancy Project as an example. The results show that the use of the joint optimization scheduling led to a 10% increase in the power generation capacity and a 15% reduction in the total energy consumption. The change in the water level was reduced by 0.25 m upstream of the Yundong Sluice, and by 50% downstream of pumping stations No. 1, No. 2, and No. 4. It is clear that the joint optimization scheduling proposed in this study can effectively improve power generation capacity of the project, minimize operating costs and energy consumption, and enable more stable operation of various hydraulic structures. The results may provide references for the management of water conservancy projects in complex river networks.     

Energy efficiency in a water supply system:Energy consumption and CO2 emission

This paper presents important fundamentals associated with water and energy efficiency and highlights the importance of using renewable energy sources.A model of multi-criteria optimization for energy efficiency based on water and environmental management policies,including the preservation of water resources and the control of water pressure and energy consumption through a hybrid energy solution,was developed and applied to a water supply system.The methodology developed includes three solutions:(1)the use of a water turbine in pipe systems where pressures are higher than necessary and pressure-reducing valves are installed,(2)the optimization of pumping operation according to the electricity tariff and water demand,and(3)the use of other renewable energy sources,including a wind turbine,to supply energy to the pumping station,with the remaining energy being sold to the national electric grid.The use of an integrated solution(water and energy)proves to be a valuable input for creating benefits from available hydro energy in the water supply system in order to produce clean power,and the use of a wind source allows for the reduction of energy consumption in pumping stations,as well as of the CO2 emission to the atmosphere.     

Domestic Water Consumption under Intermittent and Continuous Modes of Water Supply

Although an extensive literature emphasizes the disadvantages of intermittent water supply, it remains prevalent in rural areas of developing countries. Understanding the effects of water supply time restrictions on domestic water use activities and patterns, especially for hygienic purposes, is important for the elaboration of the water supply. We studied the influence of intermittent and continuous water supply on water consumption and related activities in villages in the central region of the Wei River basin, China. Data were collected from a survey of 225 households in the sampled villages. Compared with a continuous water supply of 24 h d^?1 (hours per day), adopting an intermittent water supply can reduce domestic water consumption. However, it presents risks in terms of hygiene behavior, particularly the frequency of face, hands, and feet washing, as well as water sharing among family members. Outdoor water consumption is more affected than indoor water consumption under slight supply restriction (≥6 and?<?24 h d^?1), whereas indoor water use is most affected under moderate supply restriction (>1.5 and?<?6 h d^?1). Villages with high supply restriction (≤1.5 h d^?1) meet only the minimum basic requirements for domestic use, 33.6–34.7 L c^?1 d^?1 (liters per capita per day). We conclude that the determination of the daily water delivery duration for intermittent water supply in rural communities of developing countries should give greater consideration to differences in water use activities and patterns under the water supply time restrictions.