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[Display omitted] [ABSTRACT FROM AUTHOR]

The increasing pathogenic bacteria threat in irrigation water has become a worldwide concern, prompting efforts to discover a new cost-effective method for pathogenic bacteria eradication, different than those currently in use. In this study, a novel copper-loaded porous ceramic emitter (CPCE) was developed via molded sintering method to kill bacteria from irrigation water. The material performance and hydraulic properties of CPCE are discussed herein, and the antibacterial effect against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was evaluated. The incremental copper content in CPCE improved flexural strength and pore size, which was conducive to enhancing CPCE discharge. Moreover, antibacterial tests showed that CPCE displayed efficient antimicrobial activity, killing 99.99% and more than 70% of S. aureus and E. coli , respectively. The results reveal that CPCE , with both irrigation and sterilization functions, can provide a low-cost and effective solution for bacterial removal from irrigation water. [Display omitted] • A CPCE with both irrigation and sterilization functions was developed. • CPCE effectively removes S. aureus and E. coli from irrigation water. • Flexural strength and discharge of CMCE improved as Cu content increased. • CPCE is driven by gravity and consumes almost zero energy. • CPCE provides a cost-effective method for bacterial removal from irrigation water. [ABSTRACT FROM AUTHOR]

Emitter clogging has a direct impact on the performance and service life of a drip irrigation system. A study of labyrinth emitter clogging was conducted to determine the effects of pulsating versus constant pressure on average emitter flow rate ( $$\overline{q}$$ ), the Christiansen uniformity coefficient (Cu), and the location of clogged emitters. Under constant pressure, emitters in this study began to be clogged after the 8th irrigation, whereby 15 emitters eventually became clogged; the average emitter flow rate decreased to 75% of the original emitter flow rate ( $${{q}_{0}}$$ ) after the 15th irrigation, and Cu decreased rapidly by 68.2%. For pulsating pressure, emitters began to be clogged after the 14th irrigation, only 5 emitters became clogged, and $$\overline{q}$$ only decreased to 85.3% of $${{q}_{0}}$$ , and Cu declined by only 22.6%. These results demonstrate that the anti-clogging performance of emitters with pulsating pressure is better than with constant pressure. Emitter clogging at a constant pressure generally occurred at the inlet and front of labyrinth channels, mainly due to deposition of sediment particles. Emitter clogging with pulsating pressure is due to other impurities (e.g., debris of Teflon tape) besides sediment particles plugging the labyrinth channel. Pulsating pressure is recommended for use in drip irrigation to prevent emitter clogging. [ABSTRACT FROM AUTHOR]

China's Loess Plateau is the optimal and largest region of growing apple trees in the world. Subsurface irrigation with ceramic emitters (SICE) is an energy-efficient and water-saving approach for fruit trees in arid and semi-arid regions. Climate change, which is shifting annual precipitation regimes, is challenging the existing irrigation scheduling. However, little is known about how annual precipitation change affect the irrigation scheduling with SICE. Therefore, simulations with HYDRUS-2D and validation experiments in apple orchard were used to study the effects of the event- and annual-scale precipitation and ceramic hydraulic conductivity of emitter (CHC) on soil water dynamics. Results indicated that annul precipitation slightly affected the irrigation volume, however precipitation events had a significant effect on emitter discharge; the outflow was 22.7% and 49.7% lower in soil than in air with CHC of 0.017 and 0.077 m d−1. There was a significant positive correlation among CHC, irrigation volume and deep percolation. Precipitation and CHC both have a significant effect on the soil water content in apple orchards, the average SWCs of wet year were 17.8%− 24.7% higher than normal and dry year, the average SWC was 0.154 and 0.191 cm3 cm−3 with emitter hydraulic conductivities of 0.017 and 0.077 m d−1, respectively, in 2010. SICE could provide a stable soil water environment for apple trees in different precipitation years. Apple trees could be continuously irrigated by SICE until July, and irrigation could be stopped when the average SWC exceeds 0.20 cm3 cm−3 after July in Loess Plateau. This work may assist orchard managers in adapting their orchards by SICE to meet apple growth under future climate change conditions. [Display omitted] • Precipitation could cause a reduction of emitter discharge. • Subsurface irrigation with ceramic emitter could provide a stable soil moisture environment for apple trees. • Irrigation could stop when the average soil water content exceeds 0.20 cm3 cm−3 after July in Loess Plateau. [ABSTRACT FROM AUTHOR]

BACKGROUND: Analysis of cropping patterns is a prerequisite for their optimisation, and evaluation of virtualwater flows could shed new light on water resources management. This study is intended to explore the effects of cropping pattern changes between 1960 and 2008 on virtual water flows related to crops transfer in the Hetao irrigation district, China. RESULTS: (1) The sownarea of crops increased at an average rate of 3.57×10³ ha year-1 while the proportion of sown grain crops decreased from 92.83% in the 1960s to 50.22% in the 2000s. (2) Virtual water content decreased during the study period while net virtual water exports increased since the 1980s. (3) Assuming that the cropping pattern was constant and was equal to the average 1960s value, accumulated net virtual water export in 1980-2008 would have been 4.76×109 m³ greater than that in the actual cropping pattern scenario. CONCLUSION: Cropping pattern changes in the Hetao irrigation district could not only be seen as resulting fromthe pursuit for higher economic returns, but also as a feedback response to limited water resources. A systematic framework is still needed for future cropping pattern planning by taking food security, continued agricultural expansion and other constraints into consideration. [ABSTRACT FROM AUTHOR]

The assessment of agricultural production efficiency of Hetao irrigation district of Inner Mongolia, an important agricultural production area of China, is of great significance in guaranteeing national food security. Much attention has been paid to blue water (surface and groundwater), while the use of green water (rainwater insofar as it does not become run-off) is rarely included in the agricultural production analysis. Compared to blue water, the cost of green water is less, but its environmental impact is concerned . Consequently, this paper analyzed agricultural productive efficiency of five counties in the Hetao irrigation district during 2000-2008 using data envelopment analysis (DEA) by considering blue water, green water, and other indicators. First, the technology efficiency, pure technology efficiency, and scale efficiency were analyzed combining CCR-I and BCC-I models and then some suggestions about how to adjust the amount of input resources were provided for ineffective decision making units (DMU). Results show that: among the 45 DMUs, there were 24 DMUs that were DEA-effective. The values of technology efficiency, pure technology efficiency, and scale efficiency of five counties during the period of 2005-2008 were greater than those during the period of 2000-2004. The differences of technology efficiency in different counties were not significant and the value for Qianqi (0.878) was smaller than the other four counties, which were larger than 0.9. The agricultural productivity efficiency of Qianqi was mainly influenced by production scale and it was the application of technology for Hanghou and Wuyuan. In order to be DEA-effective, the inputs of 21 DMUs should be decreased and the decreasing proportions were 16.66% (blue water), 22.23% (green water), 19.46% (irrigation areas with salinization problem), 20.66% (irrigation areas without salinization problem) and 23.82% (agricultural population). The use of different resources was inefficient and would have an adverse effect on the development of the irrigation district. To some extent, the redundancy of water and land resources in agricultural production may be related to the characteristics of green water. The rainfall in the Hetao irrigation district was uneven both temporally and spatially. Local farmers would increase the use of blue water and land resources when they were not sure about the amount of green water that the crops could use to achieve a better harvest. As a result, the use efficiency of blue water and land resources would decrease when the grain production was lower than the expectation value, which was mainly caused by the litter rainfall. The use efficiency of green water would decrease when the expectation green water was larger than actual value. In the future, the rational distribution of labor among agricultural production and other industries would be helpful in achieving a more effective agricultural production pattern for the Hetao irrigation district. Besides, the improvements of irrigation frustration and land resources management were also needed for the Hetao irrigation district. hift of cropping pattern to crops with lower irrigation water input and higher output would also be suggested considering the difficulty in decreasing the redundancy for green water. This study could provide some suggestions for the efficient agricultural production in the Hetao irrigation district and the improvement of the agricultural production system in other irrigation districts. [ABSTRACT FROM AUTHOR]

As non-point source pollution and salinization being the important environmental pollution source that affects food security, the evaluation and quantification of such negative effects on agricultural production become the urgent eco-environment issues need to be solved. It is possible to quantify the negative effects of agricultural production because of the foundation of Water Footprint Theory. Water footprint contains blue water footprint, green water footprint and grey water footprint. Grey water footprint(GWF) can represents the value of different types of negative effects, of which the GWF of grain production represents the negative effect of per unit grain production. In the study, water footprint theory is used and Hetao irrigation district in Inner Mongolia was employed as the study area. The calculation method of the grain production GWF were given and the parameters of maximum environmental allowable concentration(Cmax) and background concentration(Cnat) were selected. Each kind of GWF was calculated Item by item, and the total GWF was computed using the Cask Theory, so the GWF of grain production was calculated and analyzed. The results showed that the GWF of non-point source pollution was 0.55-0.58×108m3 during the period of 2005-2008. The GWF of salification was 4.570×108m3 in 2005 and decreased to 1.825×108m3 in 2008. The total GWF was declined from 5.872×108m3 in 2006 to 1.825×108m3 in 2008. In year of 2005-2008, the total GWF was less than 10% of total water footprint, and showed a slightly decline tend along the years. The GWF of grain production from year of 2005 to 2008 was 0.129 m3/kg, 0.159 m3/kg, 0.062 m3/kg and 0.043 m3/kg, respectively. In general, the GWF of grain production showed declining tend, which in 2008 was only equivalent to 27.04% of that in 2006. The extension of new agricultural technologies such as water-saving irrigation was the main reason, water-saving irrigation significantly reduce GWF of grain production by decreasing ineffective irrigation and invalid moisture evaporation. Based on these, the measures, including water saving, cropping structure adjustment, reasonably determination of ground water level and reasonable utilization of fertilizers and pesticides, are recommended for reducing the GWF of grain production. The negative effects of environmental issues on food production and GWF of grain production in large-scale irrigation area are quantified preferably. The results can offer a valuable reference for the agricultural sustainable development and formulating agricultural industry policy for other similar grainproducing regions. [ABSTRACT FROM AUTHOR]

Abstract: Irrigation plays an increasing important role in agriculture of China. The assessment of water resources utilization during agricultural production process will contribute to improving agricultural water management practices for the irrigation districts. The water footprint provides a new approach to assessing the agricultural water utilization. The present paper put forward a modified calculation method to quantify the water footprint of crop. On this basis, this paper calculated the water footprint of major crop in Hetao irrigation district, China. Then, it evaluated the influencing factors that caused the variability of crop water footprint during the study period. Results showed that: 1) the annual average water footprint of integrated-crop production in Hetao irrigation district was 3.91m3 kg−1 (90.91% blue water and 9.09% green water). The crop production in the Hetao irrigation district mainly relies on blue water; 2) under the integrated influences of interannual climate variability and variation of agricultural inputs, the water footprint of integrated-crop production displayed a decreasing trend; 3) the contribution rate of the climatic factors to the variation of water footprint was only −6.90%, while the total contribution rate of the agricultural inputs factors was −84.31%. The results suggest that the water footprint of crop mainly depends on agricultural management rather than the regional climate and its variation. The results indicated that the water footprint of a crop could be controlled at a reasonable level by better management of all agricultural inputs and the improvement of water use efficiency in agriculture. [Copyright &y& Elsevier]

Although the water productivity of the agricultural sector in China continuously increased over the last twenty years, by improvements in irrigation technology, the total agricultural water use did not decline as expected, mainly due to continuous increases in agricultural output partially derived from technological progress. Thus, agricultural water use in China may experience a rebound effect. This study defines the water rebound effect ( WRE ) using macro-scale indicators of water use and water productivity, establishes a simplified direct comparison method using the contribution rate of technological progress, and evaluates the magnitude of the macro-scale water rebound effect in the Chinese agricultural sector using provincial panel data from 1997 to 2014. The magnitude of the agricultural WRE in China (1998–2014) is 61.49%. The northern and western regions of China experience a greater WRE than the southern and eastern regions, and the changes in the inter-annual WRE are distinct. These observations indicate that much of the expected water savings from efficiency improvement could be offset by increased water use for increased agricultural production due to technology enhancement. The control of water use growth is effective for reducing the water rebound effect. The study confirmed the existence of the agricultural WRE in China. [ABSTRACT FROM AUTHOR]

Scarcity and competition for water are becoming matters of increasing concern around the world. The interdisciplinary nature of the problem requires that the technical, economic, environmental and social aspects of water usage are integrated into a coherent analytical framework. Therefore, a comprehensive evaluation of agricultural water use during crop production is a necessary prerequisite for agricultural water management. The present study provides an overview of water-accounting and water footprint assessment methods by analysing the performance, efficiency, economic profitability and environmental impact of the Hetao Irrigation District, China. The performance and efficiency results showed that the total volume of water consumed in the Hetao Irrigation District, during wheat production, was 872 Mm 3 , of which 116 Mm 3 was green water and 756 Mm 3 was blue water. Furthermore, 443 Mm 3 of the blue water was used effectively, while 313 Mm 3 was non-beneficial due to an inefficient irrigation system. The grey water footprint was 152 Mm 3 during wheat production, which accounted for 15.42% of the total available water in the district. The results indicated that the economic profit is higher relative to the national average due to the high yields in wheat production in the Hetao Irrigation District. However, efficient use of resources and environmental sustainability were relatively low due to high water consumption and pollution. This study highlighted the need for a comprehensive evaluation of water use in agricultural production and it provides insights by using water footprint and water accounting in water use assessment and is a reference for other related studies. [ABSTRACT FROM AUTHOR]

Irrigation plays a major role in Chinese agricultural production, as China is experiencing water and food scarcity. Assessing water use (WU) and water productivity (WP) will contribute to regional water management and grain production improvement. This paper quantifies the water use and productivity in grain production for 31 Chinese provinces, autonomous regions and municipalities (PAMs) by distinguishing between irrigated and rain-fed farmland. An indicator of marginal productivity of blue water (MWP b ) is established and calculated to evaluate irrigation profits. National water use (WU t ) for grain cultivation from 1998 to 2010 was approximately 689.04 Gm 3 (42.26% blue water and 57.74% green water). The productive water proportions for irrigated and total croplands were 65.57% and 76.85%, respectively. Water use compositions from both blue–green and productive–unproductive perspectives changed slightly over time. The water use productivity (WPU) and water consumption productivity (WPC) for integrated grain products of China during the study period were 0.747 and 0.972 kg/m 3 , respectively. The spatial distribution patterns of irrigated WPs (WPU I, WPC I ) were consistent with those for total cropland. China has achieved sufficient food supply without increasing water use. The national MWP b was estimated to be 0.673 kg/m 3 , revealing a higher increase in crop yield on irrigated land compared to rain-fed land. The northeast provinces urgently need to improve irrigation efficiency, and the North China Plain PAMs should promote rain-fed crop yield to increase grain production and control water use in the future. [ABSTRACT FROM AUTHOR]

The implementation of a virtual water trading policy at small and localized scales may potentially contribute to alleviating water scarcity and improving local water management. This study analyzed inter-county virtual water flows related to crop transfer and its relationship with water scarcity in the Hetao irrigation district during 2001–2010. The inter-county virtual water flows was 34.29 × 10 6 m 3 /y, and the largest exporter and importer were Dengkou and Qianqi counties, respectively. More than 90% of the virtual water flows originated from counties with lower water stress and was transferred to those with higher water stress. The water scarcity index (the ratio of water withdrawal to availability) was negatively correlated with virtual water balance (the difference between virtual water exports and imports). Counties with relatively high water stress benefited from the current pattern of virtual water flows, but the Hetao irrigation district lost 1.96 × 10 6 m 3 of water annually. In the future, a more accurate evaluation of virtual water flows and a comprehensive understanding of the concept of water scarcity are needed for alleviating water scarcity and forming better production and trade strategies at the scale of irrigation districts. [ABSTRACT FROM AUTHOR]

• The working pressure head of subsurface irrigation system with ceramic emitters must be higher than 20 cm. • It is better to use the soil water content uniformity to evaluate the irrigation quality of SICE. • The discharge deviation in soil is less than that in air when working pressure head is higher than 20 cm. A subsurface irrigation system with ceramic emitters (SICE) without a pump has been developed to limit energy consumption and reduce greenhouse gas emissions. Yet whether SICE can be used in low-pressure conditions has not been tested; moreover, there is no index for evaluating the irrigation quality of SICE. Laboratory experiments, with six treatments, were conducted to study ceramic emitter hydraulic characteristics in the air and soil under different working pressure heads and emitter types. The results indicated that when H increased, the emitter discharge increased linearly, and the discharge deviation decreased in the air. With increased H in the soil, the emitter discharge, soil water content, and soil water content uniformity increased, and the discharge deviation decreased. When H was greater than or equal to 20 cm, the discharge deviation in the soil was less than that in the air, and the soil water content uniformity was higher than 80 %. The soil water content uniformity could be used in the evaluation of the irrigation quality of SICE based on the reliability and convenience of observation. To make the best use of soil water potential on the outflow of the emitter, reduce the discharge deviation, and improve soil water content uniformity, the working pressure head of SICE should be higher than 20 cm. [ABSTRACT FROM AUTHOR]

The water footprint (WF) of crop production is a measure of the volumes of blue water (irrigation water) and green water (effective precipitation) consumed during crop growth. Setting the WF benchmarks of crop production in an irrigation district, exploring the optimal tillage practices, and clearly specifying blue and green water-saving potentials (WSPs) are essential for efficient utilization and reasonable allocation of agricultural water resources. However, related studies disregarded the WF benchmark setting according to tillage practices and the corresponding WSPs at the irrigation district scale. Meanwhile, the evaluation of WSP is limited to blue water. Considering summer maize and winter wheat grown in Baojixia Irrigation District (BID) of Shaanxi Province in China as the study case, this study aims to evaluate the gross irrigation WSP, actual blue and green WSPs based on crop WF simulation and WF benchmark setting for the "best" tillage practice. Eighteen water-saving tillage practice scenarios were set considering three irrigation techniques, three irrigation strategies, and two mulching practices. Results show that crop responses to different tillage practices differ. Maize WF has low sensitivity whereas wheat WF shows a significant difference following a change in irrigation techniques. In the practice under 40% deficit irrigation with no mulching, there is the highest actual WSPs, but at the cost of at least 57% reduction in crop yield. Whereas the practice of 20% deficit irrigation, furrow irrigation, and mulching has no yield reduction and relatively low WF, which can save 20% blue water and 8–12% green water in the BID, which is the optimal balance point between the yield and water consumption of the two crops. From the perspective of crop WF, this study quantified the agricultural WSPs of different water resources, and formulated a method for evaluating agricultural WSPs based on set WF benchmarks, to provide reference for building a water-saving culture, and sustainable development. [Display omitted] • Crop water footprint benchmark is set by 18 tillage practices for an irrigation district. • Responses of crop water footprint to the same tillage practice is diverse by crop. • Maximize the water-saving potential could be at the cost of production reduction. • The set water footprint benchmarks should balance yield with water-savings. [ABSTRACT FROM AUTHOR]

• The rising trend of yield was in most regions of China caused by climate change. • The decreasing trend of water footprint was more obvious in RCP8.5 scenario. • Full irrigation could mitigate the reduction in yield caused by climate change. • Increasing irrigation cannot greatly reduce the water footprint in humid regions. Agriculture is the sector most sensitive to climate change. It is of great significance to explore the response characteristics of crop water footprint (WF) in rain-fed and irrigation agriculture to climate change for guiding agricultural production. This study coupled and downscaled the meteorological data from 31 global climate models (GCMs) under two Representative Concentration Pathways (RCPs) in China, and used crop growth model AquaCrop in large scale to quantify the changes in yield and WF of maize in China from the 2030s to the 2090s. The Monte Carlo Method was used to calibrate the crop parameters in AquaCrop model, which improved the accuracy and spatiotemporal resolution of the crop model. Results showed that precipitation and temperature would increase in most regions in China, which was more obvious in the RCP8.5 scenario. Meanwhile, climate change resulted in larger crop evapotranspiration (ET c) for maize in the north than south. In the future, the increase of ET c in Southwest China would be relatively larger, while that in Northwest China would decrease. Maize yield would generally increase in most regions except for central China, where illustrated that increases in the north was greater than in the south. In terms of irrigation strategies, full irrigation could mitigate the reduction in maize yield caused by climate change. However, increasing irrigation would have fewer benefits to maize yield in humid regions compared with arid and semiarid regions in China. In addition, increasing irrigation could not greatly reduce the WF of maize in humid regions. Due to different climatic and hydraulic soil characteristics in each region, the effects of climate change and irrigation strategies on WF of maize would vary in different regions. This study provided irrigation strategies guidance to mitigate the adverse effects of climate change on agricultural production and its water use. [ABSTRACT FROM AUTHOR]

• Irrigation techniques are accounted in large-scale crop water footprint assessment. • Micro-irrigation has the lowest WF compared to furrow and sprinkler irrigation. • Crop WF benchmarks need to be set by irrigation techniques for arid zones. Improved spatial and temporal resolutions in quantification enable the water footprint (WF) in crop production to be a comprehensive indicator of water consumption in agricultural water management. In general, existing literature focus on the impact of water-saving irrigation techniques on crop yield and water consumption during the growth period at sites or experimental units, few studies yet that explicitly addresses the effect of developments in water-saving irrigation techniques on large-scale WF accounting and benchmarking. Here, we fill this gap through a case study for wheat in China over 2000–2014, during which the micro-irrigated wheat area expanded 14 times. The green and blue WFs of China's wheat per year are estimated at a 5 arc-minute resolution. For irrigated wheat, we distinguish three irrigation techniques: furrow, sprinkler and micro-irrigation. The WF benchmarks by irrigation type are further estimated separately for arid and humid zones. Irrigation accounted for 70% of annual WF in China's wheat land, while furrow irrigation dominated the national total WF. The occupation by WF under micro-irrigation was the smallest but jumped by 14 times in quantity whereas that under sprinkler halved. China's average WF per ton of wheat under sprinkler irrigation was 21% higher than that under micro-irrigation in 2014. The 20th percentile WF benchmarks of wheat under micro-irrigation was 13% and 31% smaller than that under furrow and sprinkler irrigation, respectively, in arid zones. Meanwhile, high provincial heterogeneities in terms of WF under varied distribution of irrigation techniques were also shown. The study shows possibility and importance to account for developments of water-saving techniques in large-scale crop WF estimations. [ABSTRACT FROM AUTHOR]