The water consumption reductions from home solar installation in the United States

Installation of rooftop photovoltaic (PV) solar is expected to change the electricity landscape in the U.S. through reducing greenhouse gas emissions and mitigating global warming, as well as eliminating environmental impacts from fossil fuels utilization. Given the high-water intensity of fossil fuels, nuclear, and hydropower, the transition to solar and wind energy has important implications for also reducing the water footprint of energy production. This study evaluates the reductions in the water footprint from the electricity sector at the statewide and household scales in the contiguous U.S., as well as the expected virtual water footprint of individual homes upon switching to rooftop PV solar. Through integration of the water consumption intensity of the different energy sources that contribute to the current grid electricity, the annual residential electricity consumption, and the number of households, we have established a baseline for the variations of current statewide and household water consumption in the contiguous 48 states. The average nationwide water consumption of the residential sector from the current grid electricity is estimated as 9.84 × 109 m3, while the household grid water consumption varies from 8 to 225 m3 y-1 (a nationwide average of 66 m3y-1). We estimate the household water consumption upon installing roof solar PV (3-60 m3 y-1, a nationwide average of 4.7 m3 y-1) and the expected annual reduction in water consumption (210 %-1600 %) at the household level across the U.S. The current electricity production from rooftop solar PV in the U.S. is currently about 1.5 % of the total residential electricity consumption, which infers an overall annual saving of 374 × 106 m3 based on the average national grid water consumption in the U.S. The transition to rooftop PV solar infers not only reductions in greenhouse gas emissions coupled with a major reduction in the overall water footprint, but also a transfer of the water footprint and associated environmental implications to countries overseas where most PV panels are manufactured.

Is Food Irrigated with Oilfield-Produced Water in the California Central Valley Safe to Eat? A Probabilistic Human Health Risk Assessment Evaluating Trace Metals Exposure

Reuse of oilfield-produced water (OPW) for crop irrigation has the potential to make a critical difference in the water budgets of highly productive but drought-stressed agricultural watersheds. This is the first peer-reviewed study to evaluate how trace metals in OPW used to irrigate California crops may affect human health. We modeled and quantified risks associated with consuming foods irrigated with OPW using available concentration data. The probabilistic risk assessment simulated OPW metal concentrations, crop uptake, human exposures, and potential noncancer and carcinogenic health effects. Overall, our findings indicate that there is a low risk of ingesting toxic amounts of metals from the consumption of tree nuts, citrus, grapes, and root vegetables irrigated with low-saline OPW. Results show increased arsenic cancer risk (at 10^-6 ) for adult vegetarians, assuming higher consumption of multiple foods irrigated with OPW that contain high arsenic concentrations. All other cancer risks are below levels of concern and all noncancer hazards are far below levels of concern. Arsenic risk concerns could be mitigated by practices such as blending high-arsenic OPW. Future risk assessment research should model the risks of organic compounds in OPW, as our study focused on inorganic compounds. Nevertheless, our findings indicate that low-saline OPW may provide a safe and sustainable alternative irrigation water source if water quality is adequately monitored and blended as needed prior to irrigation.

The impact of using low-saline oilfield produced water for irrigation on water and soil quality in California

The consecutive occurrence of drought and reduction in natural water availability over the past several decades requires searching for alternative water sources for the agriculture sector in California. One alternative source to supplement natural waters is oilfield produced water (OPW) generated from oilfields adjacent to agricultural areas. For over 25 years, OPW has been blended with surface water and used for irrigation in the Cawelo Water District of Kern County, as permitted by California Water Board policy. This study aims to evaluate the potential environmental impact, soil quality, and crop health risks of this policy. We examined a large spectrum of salts, metals, radionuclides (²²⁶Ra and ²²⁸Ra), and dissolved organic carbon (DOC) in OPW, blended OPW used for irrigation, groundwater, and soils irrigated by the three different water sources. We found that all studied water quality parameters in the blended OPW were below current California irrigation quality guidelines. Yet, soils irrigated by blended OPW showed higher salts and boron relative to soils irrigated by groundwater, implying long-term salts and boron accumulation. We did not, however, find systematic differences in ²²⁶Ra and ²²⁸Ra activities and DOC in soils irrigated by blended or unblended OPW relative to groundwater-irrigated soils. Based on a comparison of measured parameters, we conclude that the blended low-saline OPW used in the Cawelo Water District of California is of comparable quality to the local groundwater in the region. Nonetheless, the salt and boron soil accumulation can pose long-term risks to soil sodification, groundwater salinization, and plant health; as such, the use of low-saline OPW for irrigation use in California will require continual blending with fresh water and planting of boron-tolerant crops to avoid boron toxicity.

Water Availability for Shale Gas Development in Sichuan Basin, China

Unconventional shale gas development holds promise for reducing the predominant consumption of coal and increasing the utilization of natural gas in China. While China possesses some of the most abundant technically recoverable shale gas resources in the world, water availability could still be a limiting factor for hydraulic fracturing operations, in addition to geological, infrastructural, and technological barriers. Here, we project the baseline water availability for the next 15 years in Sichuan Basin, one of the most promising shale gas basins in China. Our projection shows that continued water demand for the domestic sector in Sichuan Basin could result in high to extremely high water stress in certain areas. By simulating shale gas development and using information from current water use for hydraulic fracturing in Sichuan Basin (20,000-30,000 m(3) per well), we project that during the next decade water use for shale gas development could reach 20-30 million m(3)/year, when shale gas well development is projected to be most active. While this volume is negligible relative to the projected overall domestic water use of ∼36 billion m(3)/year, we posit that intensification of hydraulic fracturing and water use might compete with other water utilization in local water-stress areas in Sichuan Basin.

Fluoride exposure from groundwater as reflected by urinary fluoride and children's dental fluorosis in the Main Ethiopian Rift Valley

This cross-sectional study explores the relationships between children's F(-) exposure from drinking groundwater and urinary F(-) concentrations, combined with dental fluorosis (DF) in the Main Ethiopian Rift (MER) Valley. We examined the DF prevalence and severity among 491 children (10 to 15 years old) who are life-long residents of 33 rural communities in which groundwater concentrations of F(-) cover a wide range. A subset of 156 children was selected for urinary F(-) measurements. Our results showed that the mean F(-) concentrations in groundwater were 8.5 ± 4.1 mg/L (range: 1.1-18 mg/L), while those in urine were 12.1±7.3 mg/L (range: 1.1-39.8 mg/L). The prevalence of mild, moderate, and severe DF in children's teeth was 17%, 29%, and 45%, respectively, and the majority (90%; n=140) of the children had urinary F(-) concentrations above 3 mg/L. Below this level most of the teeth showed mild forms of DF. The exposure-response relationship between F(-) and DF was positive and non-linear, with DF severity tending to level off above a F(-) threshold of ~6 mg/L, most likely due to the fact that at ~6 mg/L the enamel is damaged as much as it can be clinically observed in most children. We also observed differential prevalence (and severity) of DF and urinary concentration, across children exposed to similar F(-) concentrations in water, which highlights the importance of individual-specific factors in addition to the F(-) levels in drinking water. Finally, we investigated urinary F(-) in children from communities where defluoridation remediation was taking place. The lower F(-) concentration measured in urine of this population demonstrates the capacity of the urinary F(-) method as an effective monitoring and evaluation tool for assessing the outcome of successful F(-) mitigation strategy in relatively short time (months) in areas affected with severe fluorosis.

The effect of non-fluoride factors on risk of dental fluorosis: evidence from rural populations of the Main Ethiopian Rift

Elevated level of fluoride (F(-)) in drinking water is a well-recognized risk factor of dental fluorosis (DF). While considering optimization of region-specific standards for F(-), it is reasonable, however, to consider how local diet, water sourcing practices, and non-F(-) elements in water may be related to health outcomes. In this study, we hypothesized that non-F(-) elements in groundwater and lifestyle and demographic characteristics may be independent predictors or modifiers of the effects of F(-) on teeth. Dental examinations were conducted among 1094 inhabitants from 399 randomly-selected households of 20 rural communities of the Ziway-Shala lake basin of the Main Ethiopian Rift. DF severity was evaluated using the Thylstrup-Fejerskov Index (TFI). Household surveys were performed and water samples were collected from community water sources. To consider interrelations between the teeth within individual (in terms of DF severity) and between F(-) and non-F(-) elements in groundwater, the statistical methods of regression analysis, mixed models, and principal component analysis were used. About 90% of study participants consumed water from wells with F(-) levels above the WHO recommended standard of 1.5mg/l. More than 62% of the study population had DF. F(-) levels were a major factor associated with DF. Age, sex, and milk consumption (both cow's and breastfed) were also statistically significantly (p<0.05) associated with DF severity; these associations appear both independently and as modifiers of those identified between F(-) concentration and DF severity. Among 35 examined elements in groundwater, Ca, Al, Cu, and Rb were found to be significantly correlated with dental health outcomes among the residents exposed to water with excessive F(-) concentrations. Quantitative estimates obtained in our study can be used to explore new water treatment strategies, water safety and quality regulations, and lifestyle recommendations which may be more appropriate for this highly populated region.

The politics of assessment: water and sanitation MDGs in the Middle East

The Middle East and North Africa (MENA) is generally considered to be making adequate progress towards meeting Target 10 of the Millennium Development Goals (MDGs), which calls for halving the proportion of the population with inadequate access to drinking water and sanitation. Progress towards achieving Target 10 is evaluated by the Joint Monitoring Programme (JMP), run by UNICEF and WHO. This article shows that the assessment methodologies employed by the JMP significantly overstate coverage rates in the drinking water and sanitation sectors, by overlooking and ‘not counting’ problems of access, affordability, quality of service and pollution. The authors show that states in MENA often fail to provide safe drinking water and adequate sanitation services, particularly in densely populated informal settlements, and that many centralized water and sanitation infrastructures contribute to water pollution and contamination. Despite the glaring gap between the MDG statistics and the evidence available from national and local reports, exclusionary political regimes in the region have had few incentives to adopt more accurate assessments and improve the quality of service. While international organizations have proposed some reforms, they too lack incentives to employ adequate measures that gauge access, quality and affordability of drinking water and sanitation services.

The water crisis in the gaza strip: prospects for resolution

Israel and the Palestinian Authority share the southern Mediterranean coastal aquifer. Long-term overexploitation in the Gaza Strip has resulted in a decreasing water table, accompanied by the degradation of its water quality. Due to high levels of salinity and nitrate and boron pollution, most of the ground water is inadequate for both domestic and agricultural consumption. The rapid rate of population growth in the Gaza Strip and dependence upon ground water as a single water source present a serious challenge for future political stability and economic development. Here, we integrate the results of geochemical studies and numerical modeling to postulate different management scenarios for joint management between Israel and the Palestinian Authority. The chemical and isotopic data show that most of the salinity phenomena in the Gaza Strip are derived from the natural flow of saline ground water from Israel toward the Gaza Strip. As a result, the southern coastal aquifer does not resemble a classic "upstream-downstream" dispute because Israel's pumping of the saline ground water reduces the salinization rates of ground water in the Gaza Strip. Simulation of different pumping scenarios using a monolayer, hydrodynamic, two-dimensional model (MARTHE) confirms the hypothesis that increasing pumping along the Gaza Strip border combined with a moderate reduction of pumping within the Gaza Strip would improve ground water quality within the Gaza Strip. We find that pumping the saline ground water for a source of reverse-osmosis desalination and then supplying the desalinated water to the Gaza Strip should be an essential component of a future joint management strategy between Israel and the Palestinian Authority.