Largest Water Source Research Articles

Development of zeolite 5A-incorporated polyvinyl alcohol membrane for desalination by pervaporation

Abstract With the rapid depletion of potable and useable water resources globally due to population growth and the effects of global warming, the desalination of seawater – the world’s largest source of water – to acceptable quality levels is critical to meeting future water needs. This study investigates the use of zeolite 5A-incorporated polyvinyl alcohol membranes to produce fresh water from seawater for industrial and domestic use and evaluates the application of the pervaporation process on the separation performance. Polyvinyl alcohol and polyvinyl alcohol/zeolite 5A mixed matrix membranes were prepared by solution-casting technique, and their morphological, structural, and mechanical properties were analyzed by field emission scanning electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, and tensile strength tests. The swelling behavior and pervaporation performance of the membranes were investigated at different temperatures (30, 45, and 60 °C) using synthetic seawater containing 35 g L−1 NaCl, and membrane–solvent interactions were determined using data from sorption experiments. The membrane produced water flux and salt rejection values at 60 °C of 5.82 kg m−2 h−1 and >99.9 %, respectively.

Toponymy analysis as geosocial cultural approach on disaster mitigation studies in Sumberagung Village Pracimantoro District Wonogiri Regency

Disaster mitigation studies with a geographical, social and cultural approach can be carried out on a system of place names known as toponymy. Toponomy generally has a relationship with the characteristics of the region. Sumberagung Village, located in Pracimantoro District, Wonogiri Regency, Central Java, has a unique character as a karst area. This study aims to analyze the toponymy of Sumberagung Village which is related to the spatial, social, and cultural context as a study of disaster mitigation in the region. The research method uses descriptive qualitative analysis with interview techniques, documentation and field surveys. The results of the study show that the Toponymy of Sumberagung Village contradicts the factual conditions of the environment. The name “Sumberagung” which means a large water source has the characteristics of an area that is prone to drought. The history of the name Sumberagung Village comes from deep contemplation, prayer and hope to find a large source of water that can be used in mitigating drought. The expectation of a large supply of water forces the community and the government to make efforts which are manifested as policies, tracing karts water sources that are below the surface, and providing water resources infrastructure. These efforts show that toponymy indirectly has a relationship with disaster mitigation in Sumberagung Village.

Compressive Fracture Behavior and Acoustic Emission Characteristics of Sandstone under Constant Crack Water Pressure

Abstract Engineering rock containing flaws or defects under a large water source is frequently subject to the couple influence of constant crack water pressure and geostress. To investigate the fracture behavior of precracked rock under hydromechanical coupling with constant crack water pressure, compression tests were conducted on red sandstone specimens containing a single crack of different angles using a device to realize the constant crack water pressure during loading, and the failure process of rock specimens was monitored by acoustic emission (AE) technique. The results show that the presence of constant crack water pressure has a significant promotion effect on the development of shear wing cracks, and the promotion effect is influenced by the prefabricated crack angle and water pressure. As the constant crack water pressure increases, the failure mode of the 0° precrack specimen changes from “X”- shear failure to the single oblique shear failure along the shear wing crack direction, the main failure crack of the inclined precracked specimens (precrack angles of 15°, 45°, and 60°) changes from a small acute angle with the prefabricated crack to a direction along the shear wing crack, and irregular cracks occur at the chipped prefabricated crack in the 90° precracked specimen. With an increase in the constant crack water pressure, the average energy for a single hit, cumulative AE energy, and cumulative AE hits decrease, and the proportion of the tensile cracks increases and that of the shear cracks decreases.

Multi-Scale Remote Sensing Assessment of Ecological Environment Quality and Its Driving Factors in Watersheds: A Case Study of Huashan Creek Watershed in China

The Huashan Creek watershed is the largest water source and the main production area of honeydew in Pinghe County, whose extensive cultivation of honeydew has exacerbated soil and water pollution. However, the spatial application of remote sensing ecological index (RSEI) in this watershed and key driving factors are not clear considering the applicability of data quality and the diversity of methodological scales. To explore the RSEI and driving factors at distinct scales in Huashan Creek watershed, this study constructed the RSEI based on the environmental balance matrix at seven scales in 2020, revealed its spatial response characteristics at different scales, and analyzed the key drivers. The results show that the 240 m grid as well as rural and watershed scale convergence analyses satisfy the assessment of RSEI, whose Moran indexes are 0.558, 0.595, and 0.146, respectively. The RSEIs at different scales have significant spatial aggregation characteristics, but the overall status is moderate. The central town–riparian area with poor RSEI contrasts with the western mountainous area, which has comparatively better quality. Population has a major influence on RSEI at multiple scales (0.8), with elevation and patch index acting significantly at the village and grid scales, respectively. These findings help to identify the spatial distribution of quality and control mechanisms of RSEI in the Huashan Creek watershed and provide new insights into key scales and drivers of ecological restoration practices in the watershed.

Analysis of Seasonal Water Characteristics and Water Quality Responses to the Land Use/Land Cover Pattern: A Case Study in Tianjin, China

As the second largest city in northern China, Tianjin has a unique geographical and social status. Following its rapid economic development, Tianjin is experiencing high levels of surface water pollution. The land use/land cover (LULC) pattern has a considerable impact on hydrological cycling and pollutant transmission, and thus on regional water quality. A full understanding of the water quality response to the LULC pattern is critical for water resource management and improvement of the natural environment in Tianjin. In this study, surface water monitoring station data and LULC data from 2021 to 2022 were used to investigate the surface water quality in Tianjin. A cluster analysis was conducted to compare water quality among monitoring stations, a factor analysis was conducted to identify potential pollution sources, and an entropy weight calculation was used to analyze the impact of the land use pattern on water quality. The mean total nitrogen (TN) concentration exceeded the class Ⅴ water quality standard throughout the year, and the correlation coefficient of the relationship between dissolved oxygen (DO) and pH exceeded 0.5 throughout the year, with other water quality parameters showing seasonal changes. On the basis of their good water quality, the water quality monitoring stations near large water source areas were distinguished from those near areas with other LULC patterns via the cluster analysis. The factor analysis results indicated that the surface water in Tianjin suffered from nutrient and organic pollution, with high loadings of ammonia nitrogen (NH3N), TN, and total phosphorus (TP). Water pollution was more serious in areas near built-up land, especially in the central urban area. The entropy weight calculation results revealed that water, built-up land, and cultivated/built-up land had the greatest impact on NH3N, while cultivated land had the greatest impact on electrical conductivity (EC). This study discusses the seasonal changes of surface water and impact of land use/land cover pattern on water quality at a macro scale, and highlighted the need to improve surface water quality in Tianjin. The results provide guidance for the sustainable utilization and management of local water resources.

Advanced optimisation in pilot-scale trial and emergency pre-treatment design to produce safe drinking water

Following severe drought in 2018-19, bushfires in late 2019, and three successive extreme rain events between 2020 and 2022, the water quality in Warragamba Dam, the largest water source in Sydney, has significantly deteriorated. This resulted in a turbidity of >110 NTU and a true colour of >100 CU420, representing a significant increase of suspended particles and natural organic matter respectively in raw water, after heavy rainfall in July 2022. Through advanced testing and optimisation at the pilot-scale contact filtration plant and designing an emergency pre-treatment strategy, Sydney Water was able to produce safe drinking water (turbidity <0.20 NTU) from full-scale Water Filtration Plants (WFPs) that have contact filtration technology, to avoid potential severe impacts on 85% of Sydney’s water supply and ensure drinking water met Australian Drinking Water Guidelines, while water quality remained outside the design envelope of the plants. The novel optimisation in a pilot-scale contact filtration plant for increased suspended particles (turbidity) and natural organic matter (true colour) in raw water caused by extreme events is discussed in this paper. The increase of true colour and dissolved organic carbon (DOC) represents a significant increase of natural organic matter (NOM) in the raw water due to extreme events. The characterisation of DOC of raw water and its impact on the contact filtration water treatment process is also discussed in this paper.

Calibration of Water Inrush Channel and Numerical Simulation of Water Inrush Process in Coal Mine Roof

The surrounding rock of a coal mine roof fractures with the excavation of the underground working face in coal mining. These mining-induced fractures are connected and extended upward to form water inrush channels. A water inrush accident may occur when there is a sufficiently large water source. To elucidate the formation mechanisms of the roof water inrush channel and the characteristics of water inrush in goafs, we performed a case study of No.18401 Panel of Xiqu Coal Mine in China and determined whether the roof water inrush channel is connected by theoretical calculation and microseismic monitoring. The modified mechanical parameters of rock masses were embedded into the numerical model based on microseismic data. Microseismic monitoring and numerical simulation were organically combined to analyze the connection process of the water inrush channel, after which the roof water inrush channel is calibrated on the No.18401 Panel. We established a non-Darcy flow model for water inrush in the water-conducting fractured zone of mines by coupling the Darcy, Forchheimer, and Navier–Stokes equations. Finite element language and its compiler (FELAC) was used to study the water inrush mechanism of non-Darcy seepage. The results show that the pressure, velocity, and porosity in the water-conducting fractured zone are non-uniform in water inrush occurrence and development, and the mixed fluid mainly passes through the “dominant channel.” The development of water inrush is accompanied by the release of the hydrostatic pressure in the aquifer, the sudden increase of the velocity at the water inrush position, and the increase in fluid concentration. Hence, the underground water inrush can be predicted and prevented by monitoring the aforementioned indicators. This research is of great significance for the calibration of the water inrush channel of the roof and the prediction of water inrush disasters.

Delineation and Evaluation of Groundwater Quality by using GIS mapping system and Statistical Approaches in Southern Punjab, Pakistan

The groundwater is the second largest source of water in Pakistan. This study deals with the delineation and evaluation of spatial variations in the groundwater quality in Multan, Khanewal, Lodhran, Vehari, Pakpattan and Sahiwal district of Southern Punjab, Pakistan. The three major indicators such as EC, SAR and RSC (Electrical Conductivity, Residual Sodium Carbonate and Sodium Adsorption Ratio) are used and appraisal for irrigation to check groundwater quality via GIS, GS+ software and statistical analysis. The groundwater samples were evaluated for its applicability in irrigation and for mapping consequence . The parameters analyzed were compared with Standards that were adopted by WAPDA, PID and PCRWR. Kriging interpolation maps were delineated with three zone layers such as good (weight = 3), marginal (weight = 2) and bad (weight = 1). It was concluded that the area under marginal and hazardous groundwater quality with low weights was significantly increased from 2 to 10% and 7 to 40% in pre- and post-monsoon respectively due to EC, SAR and RSC parameters. Most of the study area (> 35%) contaminated was due to EC parameters. Most of the study area (tehsil Kabirwala) was observed with low quality against all discussed quality parameters in both season. The groundwater quality parameter weightage decreases from northeast to southwest of study region. Low weightage zones were observed in lower part of the area. It is recommended that in high vulnerability area artificial well recovery, auriferous storage and rain harvesting techniques should be adopted specially in lower part to reduce salinity of water. The policy maker should make policies about regulation of water resources with good quality for best utilization of water for agricultural and industrial use.

Design of Microhydro Power Plant Prototype Based on Kelekar River Flow Discharge

Indonesia is a country that has a very large water source, so it has the potential to develop hydro power plant as a superior resource. One of the rivers in the province of South Sumatra has the potential to be developed as a source of micro-hydro power plants, namely the Kelekar River in Ogan Ilir Regency. The existence of the Sriwijaya University Embung which is located on the Kelekar River can certainly support the use of Kelakar River water as a micro hydro power plant. The design of a prototype for a micro-hydro power plant aims to obtain a model of the tool as a reference in making a power plant tool in the field. Making prototypes of the tool refers to the results of previous research on the characteristics of the Kelekar River, namely the design discharge (Qd) of 0.45m3/sec, the effective fall height (Heff) at the embung is 3.475792 m, the water flow power is 15,344 kW, and the power (pt) produced by the turbine is 11,508 kW with the turbine efficiency (ŋt) of 0.75. The resulting discharge is 0.000145 m3/s with a transmission speed of 23.078 m/s, and the resulting energy is 4.944 Watt.

Operating redox couple transport mechanism for enhancing photocatalytic H2 generation of Pt and CrOx-decorated ZnCdS nanocrystals

Metal sulfide photocatalysts have been leading edge for hydrogen evolution reaction (HER) and solar energy conversion due to their suitable electronic and optical properties. The efficiency of these photocatalysts is mostly restricted by slow transfer of photogenerated holes and sluggish water dissociation kinetics. Here, we proposed HER catalyst comprising of Pt-CrOx sites loaded on ZnCdS nanocrystal (ZnCdS/Pt-CrOx) that employing a redox couple (OH/OH−) transport mechanism to efficiently relay of holes in alkaline media. The Pt sites provide optimal hydrogen adsorption energy and CrOx sites support water dissociation, which speed up water dissociation kinetics and leads to a noticeable enhance in HER (21.1 mmol g−1 h−1) and phenol degradation. Such efficient activity could be associated to a better mobility of redox couple and fast water dissociation kinetics in alkaline solution. These types of related works open pathways to generate hydrogen from the sea water, largest water source on earth.

Development of measures for limiting negative impacts of the «Atomic» lake on population and environment

In arid climate, economic activities at the territory of the “Atomic” lake is one of the topical issues for the Semipalatinsk test site (STS). Hence, the boundaries of areas with radionuclides contamination, which correspond to the level of radioactive wastes at the territory adjacent to the “Atomic” lake of STS, are to be determined.The territory around the lake is used for cattle breeding and the water of the “Atomic” lake that is the one large water source is used for livestock watering. It is important to develop measures that will limit possible negative impact on population and environment.In results of the conducted research were developed measures consisting of remediation and access limitation to the stockpile of soils with contamination level corresponding to the level of radioactive waste (RW).

Long-term relationship between air and water temperatures in Lake Paldang, South Korea

A long-term investigation into the relationship between air and water temperatures was conducted in Lake Paldang, which is the largest water source in South Korea, by studying hysteresis. From 1973 to 2018, the annual mean air temperature increased by 0.05°C/yr (seasonal Sen’s slope). The results of a numerical model (R > 0.86) showed that the ratios of the air and water temperatures increased (0.71‒0.77) in the rising limb and decreased (0.70‒0.76) in the falling limb. However, the intercept values were 0.13–3.52 and 6.62–7.78 in the rising and falling limbs, respectively, and hence there was a 4–5°C increase in temperature. In particular, in 2015, 2016, and 2018, the intercept values in the falling limb were ≥ 7, exhibiting hysteresis, whereby high water temperatures were slow to decline. Lake Paldang showed stronger water temperature hysteresis than its influent rivers and stream. The rising and falling limbs did not show a large difference in the extent of water temperature change (slope). However, the water temperature did not decrease rapidly, and the decrease continued for longer due to hysteresis, which is a type of inertia where the elevated temperature persists if the summer air temperature is significantly increased.

Study on Planning, Utilization and Protection of Emergency Water Source in Danyang City

In order to respond to sudden water pollution incidents of surface water sources efficiently and ensure the water demand of industry and living in Danyang City, the location of emergency groundwater sources in Danyang City was confirmed by comparison of schemes. According to the relevant emergency water supply regulations, the forecast analysis determines that the emergency water supply event is assumed to be 7 days and the emergency water supply scale is assumed to be 300,000 m3/d. The demonstration scheme of emergency water source wasput forward. The groundwater level change was analyzed by numerical simulation, and the groundwater quality is evaluated. Results of simulationshow that the pore water in Binjiang area is abundant and can be used as a medium to large water source. The groundwater quality is extremely complex, the shallow groundwater quality is poor, it is not suitable for drinking, and the deep water quality is relatively good. After treatment, it can be used as an emergency water source. Under the condition of emergency exploitation of water source area, the water level of the second aquifer group in the mining funnel area will approach - 20m, forming an obvious water level depression funnel area.

Hydrochemical and isotopic approach to dynamic recharge of a dolomite aquifer in South Africa

The dolomite aquifer is the largest water source in northern South Africa. The flow dynamics of the dolomite aquifer is investigated by using analyses of the hydro-chemical parameters and isotopes (3H, δ2H, δ18O, δ13C-DIC and 14C-DIC) of spring samples. Recharge areas of the dolomite aquifer are confirmed through interpretation of the hydro-geochemical types of the spring samples. The important role of rainfall in groundwater recharge is suggested by low Na+ and Cl− concentrations and by the δ2H and δ18O values of the spring samples. Groundwater mean residence time (MRT) and its temporal and spatial distributions within the young dolomite spring system can be analyzed using an improved lumped-parameter model based on the time series of 14C-DIC, initial 14C activities and δ13C-DIC values of the spring samples collected during the 1970s and 2000s. The results show that the spring samples have about 50–80% of the initial 14C activities and the MRTs of the dolomite spring system range from ≤10–51 years. At five spring sites, the temporal distributions of groundwater MRTs are identified to be significantly influenced by the variability of the local rainfall. At the Kuruman sites only, an increasing trend of the groundwater MRTs and the evolution of the [Ca2+]/[Mg2+] ratio along the flow direction indicate an important role of deep groundwater inflow to the spring flow. The results provide basic scientific information required for sustainable management of the dolomite aquifer.

POTENTIAL OF ENLARGEMENT OF RED NILE FISH (Oreochromis sp.) SWAMP WATER IN BANJARAN IRRIGATION AREA, PURWOKERTO, CENTRAL JAVA.

Racewaytechnological is a cultivation technology innovation that is able to increase production and productivity. Its development can be done in all areas with large water source discharge and flowing throughout the year, one of which is Banjaran Irrigation. Survey along the irrigation area of Banjaran, Purwokerto with purposive sampling technique is done with the aim to know the potential location of the application of red tilapia fish rearing technology. Land suitability matrics were obtained from the results of field measurements in Cijambe, Subang and Ponggok, Klaten which then performed matching with the results of research and literature supporting the enlargement of tilapia. Giving weight and score is done through approach of index overlay model. Red tilapia rearing atproductive racewaycan be conducted along the irrigation area of Banjaran, Purwokerto. There were 6 locations that can be utilized on one side and 5 locations that can be utilized on both sides.

Development of water saving toilet-flushing mechanisms

Wasting water in toilets flushing is the largest source of water wasting through the use of old siphon boxes. It occupies the first place in domestic consumption. This study reports two trial approaches for optimizing the flushing system design. The first one employs a rotatable blade in the bottom of the bowl. This blade pushes materials in the bowl to cross the trapway thus; less toilet flushing water can be used. The second approach depends on using a rotatable trapway such that it can be tilted down to enable discharging materials in the bowl directly by its gravity. This facilitates the discharge and reduces the flushwater amount which is just used to overcome friction and to clean the passage. Both are mechanical systems actuated by an external pedal mechanism that triggers the water flushing valve system in the same time. Real experiments revealed that the first approach needs more developments to work efficiently. Experiments with restricted conditions revealed that with using the rotatable trapway system approach, less than one liter of flushwater is sufficient. The required flushwater flow rate can be obtained directly from the water supply system without the need to install siphon boxes. This study can help more to design better water saving systems.

Optimal allocation of physical water resources integrated with virtual water trade in water scarce regions: A case study for Beijing, China

This study provides an innovative application of virtual water trade in the traditional allocation of physical water resources in water scarce regions. A multi-objective optimization model was developed to optimize the allocation of physical water and virtual water resources to different water users in Beijing, China, considering the trade-offs between economic benefit and environmental impacts of water consumption. Surface water, groundwater, transferred water and reclaimed water constituted the physical resource of water supply side, while virtual water flow associated with the trade of five major crops (barley, corn, rice, soy and wheat) and three livestock products (beef, pork and poultry) in agricultural sector (calculated by the trade quantities of products and their virtual water contents). Urban (daily activities and public facilities), industry, environment and agriculture (products growing) were considered in water demand side. As for the traditional allocation of physical water resources, the results showed that agriculture and urban were the two predominant water users (accounting 54% and 28%, respectively), while groundwater and surface water satisfied around 70% water demands of different users (accounting 36% and 34%, respectively). When considered the virtual water trade of eight agricultural products in water allocation procedure, the proportion of agricultural consumption decreased to 45% in total water demand, while the groundwater consumption decreased to 24% in total water supply. Virtual water trade overturned the traditional components of water supplied from different sources for agricultural consumption, and became the largest water source in Beijing. Additionally, it was also found that environmental demand took a similar percentage of water consumption in each water source. Reclaimed water was the main water source for industrial and environmental users. The results suggest that physical water resources would mainly satisfy the consumption of urban and environment, and the unbalance between water supply and demand could be filled by virtual water import in water scarce regions.

Kırıkkale’de yetiştirilen koyunlarda Schmallenberg virüs seroprevalansı ve bazı coğrafi özelliklerle ilişkisi

A virus, which effects ruminants, was firstly described in 2011 in Europe. There are limited information about this virus called Schmallenberg in Turkey. The aim of the present study was to determine the seroprevalance of Schmallenberg virus (SBV), which may cause major economic losses to sheep, and the association between seroprevalance and some geographical features (e.g. altitude, near a large water source) because of transmission by Culicoides spp. Blood samples from 1038 animals (969 ewes, 69 rams) in 38 flocks were collected and evaluated with a commercial ELISA kit in terms of specific antibody for SBV in centrum and eight towns of Kirikkale, where the altitudes ranges from 684 to 1219 meters. Age groups of the animals were determined as ≥2 - <4 (n= 517), ≥4 - <6 (n= 474) and ≥6 (n= 47) years old. The samples of Schmallenberg virus specific antibody detected as positive and suspected were 0.38% (4/1038) and 0.57% (6/1038), respectively. One out of four Schmallenberg virus specific antibody positive animals was ram, the others were ewes. On the other hand, one out of six Schmallenberg virus specific antibody suspected animals was ram, the others were ewes. The flocks of the animals with the virus specific antibody positive and suspected animals were not in places with the certain altitudes and the half of those flocks were not close to large water sources. Due to the limited numbers of animals with the virus specific antibody positive, no statistical analysis were performed to see the association between the seroprevalance of the virus and gender, age of the animals and the geographical features of the places. This study that is first investigation about Schmallenberg virus seroprevalence in sheep in Kirikkale, showed the presence of the virus specific antibody. It was also thought that this virus should be considered as the cause of abortion and malformed births in flocks

Configuring EM2 to Meet the Challenges of Economics, Waste Disposition and Non-Proliferation Confronting Nuclear Energy in the U.S.

General Atomics (GA) is developing a new nuclear concept called Energy Multiplier Module (EM2), which is a helium (He) cooled fast reactor with a net electrical output of 240 MW. It employs a “convert & burn” core design which converts fertile to fissile and burns it in situ over a 30-year core life. It can burn SNF from LWRs with no reprocessing, only refabrication. The core can be recycled using an AIROX-based method to remove a fraction of the fission products (FPs) but no heavy metals. The reactor is passively safe and sited below grade. It can sustain a Fukushima type station blackout or even a station blackout combined with a loss of coolant accident using only passive safety systems without radioactivity release or loss of plant. The afterheat is rejected directly to the air. It is a high temperature reactor and employs a direct closed-cycle gas turbine for 48% net efficiency. The reject heat can be released directly to air so that siting near a large water source is not required. GA is targeting a power cost in the range of 6-7 cents/kW-hr, which would make it a competitive power source even with low-cost natural gas. This ambitious power cost is achieved through high efficiency, simplicity of the direct cycle gas turbine power and relatively small subsystems that can be shop fabricated and shipped by road to the site.

Water productivity: science and practice—introduction

Ongoing rise in human population and aZuence, and socioeconomic imperatives continue to demand more eYcient and productive use of global Wnite resources. This is particularly true with water which society must share between its domestic, industrial, agricultural, environmental and recreational purposes. With socioeconomic development and greater concern for nature and the environment, more water must be allocated to non-agricultural uses. Consequently, improvements in management of agricultural water continue to be called for to conserve water, energy and soil while satisfying society’s increasing demand for crops for food and Wber, livestock, aquatic products, and forest products. During the past decades emphasis on improved agricultural water management has been on increasing irrigation water use eYciency, but more recently emphasis is also being paid to producing more with relatively less water—increasing water productivity. Furthermore, it has become important to assess the value of water used in agriculture more broadly. There is a need to Wnd ways to increase water productivity by improving biological and economic output per unit of water used in both irrigated and rainfed agricultural systems. Large amounts of water evaporate through crop plants, normally several hundred kilograms of water per 1 kg of total or economic biomass produced. Worldwide, 70% of total withdrawals from natural groundwater, rivers, and lakes are for agriculture. However, for most farmland, direct rainfall is the largest source of water. Only part of the rain or water applied is transpired by the crop, adding to crop production. The other part evaporates, or drains away from Welds. Some of the drainage Xows can be reused, and some cannot. Physical productivity improvements can thus be made by obtaining more productive transpiration from rain and withdrawals, producing more and higher value crops per unit of transpiration, reducing evaporation, and managing agricultural water deliveries and drainage better. Such opportunities are very diverse and occur at multiple scales, from plot to farm to watershed and region and at the biological, environmental and management levels. All the yield improvement research—genetic enhancement and crop and natural resource management—has made an important contribution to global increases in agricultural water productivity experienced over the last Wve decades or so. In contrast, little progress has been made in reducing evapotranspiration, the denominator in the water productivity ratio. Communicated by R. Evans.