Annual Water Savings Research Articles

Enhancing agricultural sustainability with water and crop management strategies in modern irrigation and drainage networks

Improving global food security hinges on achieving sustainable agricultural production within independent irrigation and drainage units, considering the availability of sustainable water resources. This study investigated the potential for enhancing the sustainability of agricultural production in a modern irrigation and drainage network (TIDN) area and evaluated the network's performance under various strategies. These strategies included mulching, transitioning from traditional to drip irrigation, combining mulching with drip irrigation (IDM), and reducing the crop yield gap. Utilizing 2009–2018 data and the AquaCrop model, which was both calibrated and validated, the green and blue water footprints (GWF and BWF) of dominant crops in the region's cropping pattern were assessed. The crop cultivation was prioritized based on the total and unit unsustainable BWF. The performance of TIDN was evaluated using indicators of reliability, vulnerability, system deficiency, flexibility, and sustainability. The drip irrigation had the most significant impact on reducing BWF, while mulching was more effective in decreasing GWF. The adoption of IDM led to a total annual water savings of 382.4 m3 ha−1. The 10-year average reductions in BWF from May to August ranged from 1.7 to 3.1 MCM, with approximately 88–93 % of these savings attributed to decreased water consumption in rice fields. Mulch, drip, and IDM decreased the BWF by 3.3 %, 9.4 %, and 10.2 %, respectively, compared to current conditions. The study revealed that the expansion of rice cultivation under conventional flooding irrigation was incompatible with the sustainable blue water resources available, and replacing rice with wheat could reduce the unsustainable BWF by 95–100 %. Compared to current conditions, IDM improved network sustainability by 1.2 %, while closing the yield gap improved the indicator by 24 %. The findings suggest that combining infrastructural solutions, such as updating irrigation systems, with farm management solutions, such as reducing crop yield gaps and implementing mulching, can significantly enhance the sustainability of production in intensively agricultural areas.

Impacts of Climate Change on Rainfall ‘Seasonality Index’ and Its Potential Implications on Water Savings and Reliability through Household Rainwater Tanks

This study depicts potential climate change impacts on annual rainwater savings from household rainwater harvesting using two different climate projection models; ACCESS 1.0 and CSIRO-Mk3.6. This paper also investigates potential changes in the relationships of ‘water saving efficiency’ and reliability with rainfall ‘seasonality index’ under the mentioned climate change scenarios. The annual water savings were calculated for three weather conditions: dry, average, and wet. Historical daily rainfall amounts provided by the Australian Bureau of Meteorology were used for three locations within the city of Brisbane (Australia). For the same locations, projected future daily rainfall amounts were collected from an online data portal facilitated by the Australian government. Potential annual water savings, water saving efficiency, and reliability values for the selected locations were calculated through a widely used tool, eTank, developed on water balance methodology at a daily scale. It was found that for the coastal location, Manly, the future water savings are not likely to change significantly. However, for the inland location, Sunnybank, the future water savings are expected to decrease under all the weather conditions through both the considered climate projections. For the far inner location, Oxley, the water savings are likely to decrease in the dry year, whereas in wet year, they are likely to increase. Also, it was found that the overall average relationship of SI–water saving efficiency is steeper for ACCESS 1.0 projected data compared to that produced through CSIRO-Mk3.6 data, and that significant differences exist among individual relationships for each location. The overall reliabilities calculated through the model projected data show lower values compared to the reliabilities calculated using historical data.

Rainwater Harvesting System Analysis for Semi-Arid Climate: A Daily Linear Programming Model

Rainwater harvesting has proven to be an alternative water supply scheme for sustainable water management of regions with limited water resources. In this paper, a linear programming (LP) model with daily time steps, which minimizes a rooftop rainwater harvesting system (RWHS) cost, is developed and used to calculate the optimum RWH tank size. The developed LP model is applied to the semi-arid Northern Cyprus in the Eastern Mediterranean. The analysis is carried out for 33 sites which receive average annual rainfall ranging from 292 mm to 548 mm to evaluate the spatial effect of rainfall characteristic and the water cost on the financial feasibility and performance of the RWHS. At 29 out of 33 sites, RWHS investments are found to be financially feasible with discounted payback periods ranging from 12 to 28 years. The optimum RWH tank sizes are determined to be between 2 m3 and 6 m3 resulting in up to 20 % reliability with more than 50 m3 of average annual water savings per house. It is observed that the cost of water is a critical factor that affects the financial feasibility and water savings of a RWHS, especially in regions with limited rainfall. The comparison of the developed daily LP model with an LP model with monthly time steps demonstrates that the financial feasibility and the optimum tank size can only be assessed realistically when daily time steps are used. Finally, the sensitivity analysis shows that the discounted payback period is highly sensitive to the collector area.

Arid AREAS Water-Piled Photovoltaic Prevents Evaporation Effects Research

(1) Background: In arid and semi-arid reservoirs, water surface evaporation is the main method of water dissipation in order to inhibit the evaporation of water and enhance economic efficiency. The evaporation inhibition rate of water-piled PV at different times of the year is derived from the anti-evaporation test of water-piled PV, and a new idea is proposed for water conservation in plains reservoirs in arid areas. (2) Methods: The test was conducted by dividing the area into groups A and B, with and without PV panel shading. In situ observation and numerical calculation were used to measure the atmosphere’s temperatures, test group, and PV module. The saturated water vapor pressure difference was then calculated according to Dalton’s principle to analyze the economic benefits of water saving. (3) Results: Based on the test results, it was found that the shading of PV panels had a cooling effect on the water body, the PV module, and the atmosphere. Group A showed a 44.2% decrease in the saturation water vapor pressure difference compared to Group B. The maximum evaporation suppression rate of 40.2% was observed in July, while the minimum rate of 12.2% was observed in January. The average evaporation suppression rate for the entire year was 29.2%. By utilizing the annual water savings for agricultural irrigation, it is possible to cover 38 hm2 of land and generate a revenue of 39,000 CNY. (4) Conclusions: The photovoltaic water cover can effectively reduce water evaporation and generate economic benefits.

Climate Change Impacts on Rainwater Tank’s Potential Water Savings, Efficiency and Reliability Presenting Relationship Between ‘Seasonality Index’ and Water Savings Efficiency

The paper presents potential impacts of climate change on rainwater tanks outcomes such as water savings, reliability and water savings efficiency under two projected climate change scenarios; RCP4.5 and RCP8.5 utilising a case study using rainfall data from four stations within the city of Brisbane, Australia. Historical rainfall data were collected from the Australian Bureau of Meteorology website for the selected stations. Projected daily rainfall data were collected from Australian government data portal for the same stations within Brisbane. Using an earlier developed daily water balance model, eTank potential annual water savings were calculated for several weather and climate change scenarios with varied roof areas and rainwater demandValues of ‘Seasonality Index (SI)’, a commonly used factor representing rainfall variability within a year, were explored to validate earlier developed relationships between SI and water savings efficiency through rainwater tanks. It is found that in most cases water savings in future periods are expected to decrease and such decrease is not necessarily attributed to the expected decrease in rainfall amounts in future, rather also affected by future reductions in rainwater tank reliability. Linear relationships between potential future water savings and reliabilities for all the stations are found. Relationship between SI and water savings efficiency was established, and it is found that the relationship slightly varies with an earlier developed relationship using historical data. Compared to earlier established relationship, for lower SI values water savings efficiency is expected to become better, while for higher SI values the water savings efficiency is expected to become worse. Also, an increase of roof area from 100 m2 to 200 m2 will cause an average increase of water savings efficiency by 25% and an increase of rainwater usage from 200 L/day to 300 L/day will cause an average increase of water savings efficiency by 20%.

Spatial and Climatic Variabilities of Rainwater Tank Outcomes for an Inland City, Canberra

Most of the studies on rainwater harvesting analysis present the outcomes for particular cities, representing a single set of results for a specific city. However, in reality, significant spatial and weather variabilities may exist, due to which presenting only one set of results for a particular city would be misleading. This paper presents the potential weather and spatial variabilities on the expected water savings and supply reliability through the domestic rainwater tank for an inland city. An earlier-developed daily water balance model, eTank, was used for the calculations of annual water savings and reliability. An Australian inland city, Canberra, was selected as a case study and relevant daily rainfall data were collected from the Australian Bureau of Meteorology website. For the analysis of spatial variation, two rain gauge stations within the city of Canberra were selected. For each station, from the historical data, three years were selected as dry, average and wet years. For each weather condition, annual water savings and reliabilities were calculated for different demands with different tank sizes up to 10,000 L connected with different roof sizes. Then, variations in annual water savings and reliabilities among different weather conditions, as well as among different stations, were evaluated. It was found that, with regard to annual water savings, a maximum variation of 68.6% can be expected between dry and wet weather; however, only a 15.4% maximum spatial variation is expected among the selected stations. Regarding reliability, a maximum variation of 123% is expected between dry and wet weather. Whereas, only a 17% spatial variation is expected among the selected stations. Such a study will provide valuable insights for rainwater tank users and stakeholders on potential variabilities due to weather and spatial differences.

Utilization of water conserved by interprovincial renewable energy substitution for thermal power: Incremental benefits and advanced reservoir operation rules

Renewable energy has been rapidly developed and transmitted across provinces to accelerate carbon neutrality in China. Water has been saved in power-receiving regions due to interprovincial renewable energy substitution for water-intensive thermal power (RST). The re-utilization of the water saved by RST through various ways is an urgent issue to be addressed. To establish the correlation between the saved water and related source reservoir and further utilize the saved water to maximize its incremental benefits, a general model framework is proposed to quantify the saved water and reallocate it to cope with emergency events and promote hydropower-based reservoir operation. The model is applied to an energy-water system centered around Henan Province. The incremental benefits and optimal reallocation mode of the saved water have been revealed. The results indicate that RST produces an annual water savings of 175.160 million m3 in Henan Province, which contributes to the increase in hydropower generation and emergency water supply ranging from 14.584 GWh to 32.267 GWh and 0 to 1.724 × 108 m3, respectively, under different hydrological scenarios. To boost the incremental benefits of water reallocation under RST, the source reservoir should concentrate on the emergency water supply in dry years and enhance hydropower generation in wet years. Conserving the saved water for future use would produce additional 12.771 GWh to 22.324 GWh of hydropower generation in the following year. As RST capacity increases from 40 to 320 TWh, the marginal revenues of hydropower generation and emergency water supply decrease by 75.4% and 40.7%, respectively, in wet years. This indicates that water supply from different sources should be rearranged to maximize total benefits according to the volume of water saved by RST and the marginal revenue characteristics. The general framework can be extended to other energy-water systems to assess incremental benefits and propose adaptive reservoir operation rules, which provides new insights into water management from the perspective of renewable energy substitution.

Implementing rainwater harvesting systems as a novel approach for saving water and energy in flat urban areas

Implementation of rainwater harvesting systems (RHS) is an effective approach to tackle increasing water and energy shortages for sustainable urban development. However, water and energy saving executions of RHS are rarely explored together in cities. This study explores the water and energy saving and economic performances of RHS in the four cities (Islamabad, Lahore, Peshawar, and Khanpur) under different climate zones of Pakistan. Three water demands (lawn irrigation, toilet flushing, and their mixture) were evaluated. Results indicated that higher annual water savings of RHS were associated with larger tank-sizes and lesser water demands in humid region. Differently, higher annual energy savings of RHS were related to greater energy consumption for groundwater pumping and larger tank sizes. At Islamabad, a 20 m3 RHS can achieve 126 m3 of annual water savings and 80% time reliability for mixed water demand, but only 23 m3 of annual water savings and 10% time reliability at Khanpur. At Lahore, a 20 m3 RHS can attain 119 kWh of annual energy savings for mixed water demand, but only 20 kWh at Khanpur. The economic viability of RHS was confirmed through adequately designed RHS at Islamabad, Lahore, and Peshawar, but except Khanpur due to its lower benefit-cost-ratio than 1.0.

Water-Saving Benefit Model Analysis of Plain Reservoirs in Arid Areas Based on Nonlinear Data Prediction under Floating Ball Cover

In order to reduce the ineffective evaporation of plain reservoirs in arid areas, strengthen the effective utilization of water resources, and explore effective water-saving benefit models. Research methods: Field tests were carried out with antievaporation floating balls with different coverage rates, and the water-saving rate and economic benefits under floating ball coverage were analyzed. By analyzing the frequency of different wind speeds, daily evaporation under different coverage rates, monthly evaporation inhibition rates under different coverage rates, and the cost of materials used were analyzed. The results showed that (1) during the test period, the total evaporation from the water surface of different cover groups was 149.5 mm, 122.2 mm, 100.1 mm, 81.1 mm, and 63.1 mm, respectively, and the evaporation inhibition rates of different cover groups were 18.4%, 30.8%, 43.4%, and 58.6%, respectively. (2) Comprehensive consideration of the preliminary input and output ratio of the latter determine when the float coverage rate of 50% is the optimal coverage rate, the annual water savings of 5421.86 m 3 , the annual increase in production value of 87,700 yuan, and the float in the reservoir site operation for 5 years to reach the recovery period and start to profit. (3) Based on the analysis of the economic indicators of laying floating balls in a large area of the reservoir and the calculation of the sales income and total investment, the results show that the total investment is a sensitive factor, and the project has a strong risk resistance ability. Therefore, the floating ball covering method to inhibit the ineffective evaporation of water surfaces is practical and feasible in terms of reservoir water-saving and economic benefits.

Pioneer attempt of incorporating four variables in generalised equations for predicting water savings through rainwater tanks

ABSTRACT This paper presents the development of robust equations for calculating expected water savings through rainwater tanks, which are dependent on annual rainfall, rainwater demand, tank size and roof area. The city of Brisbane (Australia) was selected for this purpose. A modified version of the earlier developed daily water balance model, eTank was used to calculate annual water savings under different scenarios using daily rainfall data collected from the Australian Bureau of Meteorology. Several sets of charts on varying roof size, demand, tank size and annual rainfall were produced from the simulated results. Eventually, the sets of charts were converted to a single generalised equation, each for one of the four selected regions in Brisbane. Results from the developed equations were seen matching with the model (eTank) simulated results. Such equations can be easily incorporated into mobile apps or computer programs to help quick calculations for expected water savings.

Improvement of Rainwater Harvesting Analysis Through an Hourly Timestep Model in Comparison with a Daily Timestep Model

For the analysis of rainwater tank outcomes, some researchers used monthly water balance model, which ignores an important factor such as overflow from the tank. Recently, to improve the accuracy of such analysis facilitated by the availability of daily rainfall data, many researchers started using daily timestep models. In the daily timestep models, the daily rainwater demand is deducted from the available storage, once in a day and there are debates on whether to apply that deduction at the beginning of the day or at the end of the day. Moreover, there is significant diurnal variation of water demand, which can not be accounted for in a daily timestep model. To overcome this, current study investigates an hourly timestep model considering hourly rainfall data and hourly variable rainwater demands. Hourly rainfall data was collected from the Australian Bureau of Meteorology for a raingauge station located in Melbourne. An earlier developed daily water balance model was converted to hourly scale incorporating hourly variable rainwater demands. Model simulated results for three distinct years (dry, average and wet) were compared with the results using a daily timestep model with the same data. Variations of water savings and overflow amounts are presented under four combinations of roof area and daily rainwater demand with tank sizes varying from 2500 L to 20,000 L. It is found that in all the selected years, the daily timestep model underestimated the annual water savings compared to the hourly timestep model and the highest difference was estimated to be 13,750 L for a smaller tank size connected with a bigger roof having higher rainwater demand.

Scenario Analysis of Water-Saving Potential in Yeast Manufacturing Industry under the Guidance of Water Intake Quota

While yeast manufacturing consumes a large amount of water per unit of product, water use efficiency varies widely within the industry due to disparity in water-saving technologies. By stipulating water intake per unit of product, the Norm of Water Intake––Part 41: Yeast Production (GB/T 18916.41-2019) will standardize production water use and improve the water-saving level of the yeast manufacturing industry. This paper estimates the industry’s production capacity from 2020 to 2024 through regression analysis. It examines the distribution of water use efficiency under different policy scenarios based on the standard for water intake, including the business-as-usual scenario, the bottom-line scenario, the ideal scenario, and the expected scenario. Then, the water use of the yeast manufacturing industry under different scenarios is calculated, and the water-saving potential is analyzed by comparing it with the business-as-usual scenario. The results indicate that depending on the intensity of policy implementation, the average annual water savings will range from 2.5 × 106 m 3 to 14 × 106 m 3 . The cumulative water savings will add up to 16 × 106 m 3 to 51 × 106 m 3 in the next five years, which is very large.

Superiority of water balance modelling for rainwater harvesting analysis and its application in deriving generalised equation for optimum tank size

In an urban setup optimum size of rainwater tank is a critical factor, as the space required for the rainwater tank is limited and expensive. Several methods have been used for the analysis of potential rainwater harvesting. Some authors used Rippl method for rainwater tank sizing. However, through Rippl method, required size often becomes too big and not feasible in an urban space. This paper presents a water balance modelling concept for rainwater harvesting analysis and its application in determining optimum tank size for rainwater harvesting. Results of the daily water balance model were compared with an earlier study results through Rippl method using daily rainfall data for the city of Nablus (Palestine). Daily rainfall data was collected for the city and from the collected data, three years were selected as dry, average and wet years. Using a typical average rainwater demand and the roof sizes used in the published study, and daily rainfall data for the selected years, annual water savings were calculated for varying tank sizes. From the simulated results, it is clear that for tank sizes beyond certain threshold volumes, annual expected water savings remain unchanged. It is found that Rippl method calculated optimum tank sizes are almost double the optimum tank sizes determined through eTank simulations. Finally, several optimum tank sizes were calculated for different roof sizes and demands considering an average weather condition. It is found that the optimum tank sizes can be correlated with the roof size and rainwater demand, which can be incorporated into a single generalised equation for optimum tank size. The equation calculated results are very close to the original optimum tank sizes found through manual calculation.

Reduction of water consumption in thermal power plants with radiative sky cooling

Evaporative wet cooling and dry cooling are gradually replacing water-intensive, thermally polluting once-through wet cooling in thermal power plants. Widespread adoption of evaporative wet cooling increases water losses to the atmosphere and still requires uninterrupted makeup water. Dry cooling substantially increases auxiliary power consumption and causes plant efficiency penalty. Therefore, efficient water-saving cooling technologies are of great importance. Here, we explore the water saving potential of day-night radiative sky cooling with and without evaporative wet cooling in thermal power plants. With a radiative cooling system size of 0.0055 km2/MWth normalized by the condenser thermal load at design, we show that a hybrid evaporative-radiative cooling system yields annual water savings of 30–60% in the dry and hot southwestern United States and 50–90% in other parts of the country without causing efficiency penalty. Furthermore, 100% water saving is achievable if the radiative cooling system functions as a stand-alone cooling system, with a much lower efficiency penalty and auxiliary power consumption than that of stand-alone dry cooling systems.

Assessing the Viability of Rainwater Harvesting System for Sustainable Manufacturing in Water Stressed Regions

Water is considered to the life wire of many manufacturing industry. Water is used for processing of materials, cooling of engines, firefighting and also important for sanitation and welfare of workers. As the population of the world increases, the demand for water to meet domestic and industrial needs of man increases. In line with sustainable development, there is need for practices in manufacturing which will help preserve scarce resources for domestic needs. The global trend in industries is sustainable manufacturing which is hinged at increasing operational efficiency and as well reducing cost and wastages. As a result, there is a growing interest on rainwater as an alternative source. In this paper, the rainwater harvesting system was assessed to establish its viability for a small scale pozzolana plant for sustainable manufacturing. The methodology adopted was estimating water consumption in the production plant and potential harvestable rainwater from the roof top. The harvestable rainwater was estimated based on the rainfall data obtained from the Famine Early Warning Systems Network (FEWS NET) and the rooftop (catchment) area was determined by taking dimensions of the rooftop to establish the area while a collection efficiency of 90% was assumed. Design and operational parameters from literature was used to describe the effectiveness of the system for the study area. Results revealed that water demand to run the plant for production and sanitation for staff welfare can be covered substantially using rainwater with a reliability of 99.7% and annual water savings of 1,350,000.00. The investment is viable and will be amortized in only 1.6 years. The rainwater harvesting system will generate economic benefits by reducing the cost of production and consequently the selling price will be reduced for consumers.

The development of a generalised equation for the annual water savings through rainwater tanks under different climatic conditions for southwest Brisbane (Australia)

Optimisation of rainwater tank outcomes has been a challenge for the users, as the water savings and reliability depend on many factors such as rainfall amount, rainfall distribution, tank size, roof area and rainwater demand. Among the analysis methods, daily water balance modelling is the most reasonable and acceptable approach. However, general end-users can hardly interpret/grasp the outcomes of such analyses. To overcome this hurdle, this paper presents the development of a generalised equation for calculating expected water savings through rainwater tanks with major contributing factors like rainfall, rainwater demand, tank size and roof area for southwest Brisbane (Australia). Daily rainfall data was collected for the station, Oxley which is in southwest Brisbane from the Australian Bureau of Meteorology website. The expected annual water savings for different combinations of rainfall, tank size, roof area and demand are presented in the form of charts that were converted to a generalized equation having independent variables of rainfall, tank size, roof area and demand. Results from the developed equation were seen matching with the model (eTank) simulated results. Such an equation can be easily incorporated into mobile apps or computer programs to help quick calculations for expected water savings.

Cross-sectoral implications of the implementation of irrigation water use efficiency policies in Spain: A nexus footprint approach

Abstract One technical solution often suggested for alleviating water scarcity is to increase the efficiency of irrigation water use. In Spain, several plans have been launched since 2000 to upgrade irrigation infrastructures and thereby achieve water savings equivalent to 2500 hm3/year and promote rural development. The present study uses a footprint approach to evaluate the impacts on land, water, energy, and carbon emissions of the implementation of irrigation modernization policies in agriculture in Spain between 2005 and 2011. The results show that during the period studied, the irrigated area remained stable (+0.3%), although there was a shift in crop patterns, with low-value non-permanent crops being replaced by high-value permanent crops. The water demand for irrigation decreased by 21%; half of this is explained by the shift in crop patterns and the reduction of the consumptive fraction (i.e., blue water footprint), and the other half by the cutback of return flows associated with the higher efficiency of the irrigation infrastructure. Changes in water demand have been accompanied by a progressive substitution of surface water for groundwater. Reduced water demand for irrigation has brought a reduction of 13% in water’s energy footprint and 25% in its carbon footprint. In relative terms, water efficiency (m3 consumed/m3 irrigated) has increased by 8%, although this has also increased the energy intensity (kWh/m3) to 9%. The emission rate (kgCO2 equiv/m3 irrigated) has decreased by 12% as a result of the drop in the emission factor of electricity production. Overall, irrigation modernization policies in Spain have supported the transition from an irrigation sector that is less technified and heavily dependent on surface water into one that is more productive and groundwater-based. From a resource-use perspective, such transition has contributed to stabilizing or even decreasing the irrigated land, and surpass the annual water savings target of 2500 hm3, although it has also made the sector more energy-dependent. Despite the overall positive outcomes, the observed water savings are masked by various synergistic factors, including favorable climatological conditions toward the end of the study period, which contributed strongly to curbing overall irrigation water demand. In the light of the higher frequency of observed droughts in Spain, the investments done so far do not guarantee that the planned water saving targets can be sustained if not complemented with additional measures like restricting irrigated area and/or setting caps for water intensive crops.

Water Savings Efficiency of Counterweighted Spheres Covering a Plain Reservoir in an Arid Area

Plain reservoirs in arid areas typically have long dams, large water areas and shallow water depths. Considerable evaporation loss occurs from these reservoirs. To suppress evaporation, this work adopts counterweighted HDPE spheres with diameters of 100 mm as plain reservoir anti-evaporation materials. The main purpose of this work is to study the factors that influence evaporative loss from a water surface covered by spheres and the annual water savings efficiency of the spheres. In this work, pans A and B, with areas of 1 m2 (pan A was completely covered by spheres, and pan B was uncovered), were selected to study the effects of microclimate changes on evaporation from openings among the spheres. The water temperature difference at different depths in pan A was significant, and there were significant differences in the temperature of the water surface, the air temperature near the water surface, and the relative humidity in the two pans. The factors affecting the wetted area of spheres were studied using spheres of different areas covering the reservoir. In this study, the annual water savings efficiency of the counterweighted spheres per unit area coverage was obtained by developing an evaporation calculation model. The results showed that when the coverage area of the counterweighted spheres increased from 1 m2 to 4 m2, the annual water savings efficiency per unit area increased from 69.71% to 75.42%. An economic analysis was performed to assess the viability of spheres under the current conditions of water pricing and in the given ecological context in Xinjiang.

Performance of water efficiency measures in commercial buildings

Water efficiency certification systems ease communication between all interested parties of building projects but do not provide information about the life cycle costs of water efficiency measures nor warrant a level of water efficiency performance. The present study aims at understanding of the effective performance of water efficiency solutions in commercial buildings by reporting and analyzing a specific case study - Colombo Shopping Center. The water efficiency measures implemented in Colombo Shopping Center were the following: (i) in 2008, the restrooms fixtures were replaced by more efficient models; (ii) in 2011, a rainwater harvesting system (RWHS) was introduced for supplying the cogeneration plant; and (iii) also in 2011, a greywater reuse system (GWS) was installed to use the cooling towers purged water to supply the toilets of four restrooms. The methodology included collecting the water metering records and the accounting archives since 2006, assessing the water savings and evaluating the partial life cycle costs of each measure. The partial life cycle cost analysis covers the acquisition and the first years of the operation and maintenance stages. The restroom fixtures present the highest annual water savings along with longest payback period (> 15 years), since both the investment and maintenance costs are high. The estimated payback period for the RWHS is roughly 10 years. The GWS was paid in just over 2 years and has annual water savings similar to the RWHS.

Reduction of Water Waste in an Organic Chemistry Laboratory Using a Low-Cost Recirculation System for Condenser Apparatus

A low-cost and easy-to-use water recirculation system for a condenser apparatus was designed and installed in an organic chemistry teaching laboratory. Relying on gravity and a small pump for water circulation, it supplies four stations simultaneously. The water recirculation system works very well with condensers used for distillation and reflux reactions, as well as with rotary evaporators. This innovative idea has led to an annual water savings of more than 14 400 L while running only 2 lab periods per week with up to 24 students per period. Its low cost and easy installation make it convenient and easily adoptable by any laboratory where the waste of water from condensers needs to be addressed, especially in places where water scarcity is already hindering such significant scientific activities.