Yubao Wang

The impacts of interannual climate variability and agricultural inputs on water footprint of crop production in an irrigation district of China

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 3.91 m(3)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.

The virtual water content of major grain crops and virtual water flows between regions in China.

BACKGROUND The disproportionate distribution of arable land and water resources has become a bottleneck for guaranteeing food security in China. Virtual water and virtual water trade theory have provided a potential solution to improve water resources management in agriculture and alleviate water crises in water-scarce regions. The present study evaluates the green and blue virtual water content of wheat, maize and rice at the regional scale in China. It then assesses the water-saving benefits of virtual water flows related to the transfer of the three crops between regions. RESULTS The national average virtual water content of wheat, maize and rice were 1071 m(3) per ton (50.98% green water, 49.02% blue water ), 830 m(3) per ton (76.27% green water, 23.73% blue water) and 1294 m(3) per ton (61.90% green water, 38.10% blue water), respectively. With the regional transfer of wheat, maize and rice, virtual water flows reached 30.08 Gm(3) (59.91% green water, 40.09% blue water). Meanwhile, China saved 11.47 Gm(3) green water, while it consumed 7.84 Gm(3) more blue water than with a no-grain transfer scenario in 2009. CONCLUSION In order to guarantee food security in China, the government should improve water productivity (reduce virtual water content of crops) during the grain production process. Meanwhile, under the preconditions of economic feasibility and land-water resources availability, China should guarantee the grain-sown area in southern regions for taking full advantage of green water resources and to alleviate the pressure on water resources.

An evaluation of the water utilization and grain production of irrigated and rain-fed croplands in China

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 (MWPb) is established and calculated to evaluate irrigation profits. National water use (WUt) 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 (WPUI, WPCI) were consistent with those for total cropland. China has achieved sufficient food supply without increasing water use. The national MWPb 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.

Dry/wet climate zoning and delimitation of arid areas of Northwest China based on a data-driven fashion

The division of arid areas is important in water and land resources management, planning and for a long-term agricultural, economic and social planning. Northwest China (NW) dominates the main arid areas in China. There is thus a need to adopt adequate concepts relative to the scope of arid areas of NW China and identify its climate types and characteristics. In this study, we analyzed climatic data over the last 30 years (1981–2010) from 191 stations in three provinces and three autonomous regions of NW China. The factor-cluster analysis technique (FC), an objective and automated method was employed to classify the dry/wet climate zones. The traditional methods with predefined thresholds were adopted for providing a comparison with FC. The results showed that the wet/dry climate zones by FC were mainly distributed along mountains, rivers and desert borders. Climate-division boundaries relied heavily on the major terrain features surrounding the grouped stations. It also showed that the climate was dry in the plain sandy areas but relatively wet in the high mountain areas. FC method can reflect the climate characteristics more fully in NW China with varied and complicated topography, and outperform the traditional climate classifications. Arid areas of NW China were defined as four climate types, including five resultant classes in FC classifications. The Qinling and Da Hinggan Mountains were two important boundaries, besides main administrative boundaries. The results also indicated that there are some differences between two traditional classifications. The precipitation moved and fluctuated to an extent, which confirmed that climate change played an important role in the dry/wet climate zoning, and the boundaries of dry/wet climate zones might change and migrate with time. This paper is expected to provide a more in-depth understanding on the climate characteristics in arid areas of NW China, and then contribute to formulate reasonable water and land management planning and agricultural production programs.

Evaluation of crop production, trade, and consumption from the perspective of water resources: A case study of the Hetao irrigation district, China, for 1960–2010

The integration of water footprints and virtual water flows allows the mapping of the links between production, trade, and consumption and could potentially help to alleviate water scarcity and improve water management. We evaluated the water footprints and virtual water flows of crop production, consumption, and trade and their influencing factors in the Hetao irrigation district in China for 1960-2010. The water footprint of crop production and the export of virtual water fluctuated but tended to increase during this period and were influenced mainly by agricultural factors such as crop yield, irrigation efficiency, and area sown. The water footprint of crop consumption and the import of virtual water increased during 1960-1979 and decreased during 1980-2010 and were influenced by socio-economic factors such as total population, the retail-price index, and the proportion of the population in urban areas. Most of the water footprint of production was exported to other areas, which added to the pressure on local water systems. The import of virtual water led to a saving of water for the Hetao irrigation district, while its share of the water footprint of consumption has decreased significantly since 1977. An increase in irrigation efficiency can alleviate water scarcity, and its application should be coupled with measures that constrain the continued expansion of agriculture. Full-cost pricing of irrigation water was an effective policy tool for its management. Re-shaping regional water-production and water-trade nexuses by changing crop structures could provide alternative opportunities for addressing the problems of local water scarcity, but the trade-offs involved should first be assessed.

A drought hazard assessment index based on the VIC–PDSI model and its application on the Loess Plateau, China

Drought is a complex natural hazard that is poorly understood and difficult to assess. This paper describes a VIC–PDSI model approach to understanding drought in which the Variable Infiltration Capacity (VIC) Model was combined with the Palmer Drought Severity Index (PDSI). Simulated results obtained using the VIC model were used to replace the output of the more conventional two-layer bucket-type model for hydrological accounting, and a two-class-based procedure for calibrating the characteristic climate coefficient (Kj) was introduced to allow for a more reliable computation of the PDSI. The VIC–PDSI model was used in conjunction with GIS technology to create a new drought assessment index (DAI) that provides a comprehensive overview of drought duration, intensity, frequency, and spatial extent. This new index was applied to drought hazard assessment across six subregions of the whole Loess Plateau. The results show that the DAI over the whole Loess Plateau ranged between 11 and 26 (the greater value of the DAI means the more severe of the drought hazard level). The drought hazards in the upper reaches of Yellow River were more severe than that in the middle reaches. The drought prone regions over the study area were mainly concentrated in Inner Mongolian small rivers, Zuli and Qingshui Rivers basin, while the drought hazards in the drainage area between Hekouzhen–Longmen and Weihe River basin were relatively mild during 1971–2010. The most serious drought vulnerabilities were associated with the area around Lanzhou, Zhongning, and Yinchuan, where the development of water-saving irrigation is the most direct and effective way to defend against and reduce losses from drought. For the relatively humid regions, it will be necessary to establish the rainwater harvesting systems, which could help to relieve the risk of water shortage and guarantee regional food security. Due to the DAI considers the multiple characteristic of drought duration, intensity, frequency, and spatial extent, and because it is based on the VIC–PDSI model and GIS technologies, the DAI could provide some new way on directly comparing the drought hazards over different regions during a long-term period. The result of this study may be useful to decision makers when formulating drought management policies to alleviate the risk of water shortages and guarantee regional food security.

Alleviating Pressure on Water Resources: A new approach could be attempted

Water and food safety are two major challenges which the world faces today. Traditional water management focuses on the reduction of water use through improvements in water saving technologies. However, quantitative research is needed to evaluate the effects of changing food consumption patterns on water resources. Here we report the water saving effects of changing diet pattern of the major crops and animal products in mainland China. By using the concepts of water footprint (WF) per weight unit and per calorie unit, provided by 13 primary crop and animal products, the WFs of the 13 agricultural products in each province are compared, and their water/energy conversion efficiencies are analyzed. Then, impacts of different scenarios of changing diet pattern on water consumption were explored. Results show that there are obvious differences between the WF per weight and calorie unit provided by crop and animal products due to the nutritional properties of the agricultural products. Promoting water savings from the food consumption side could give a positive feedback on water consumption. Scenario analysis of adjustments to the diet pattern proves that it is potentially feasible to reach the objective of alleviating stress on water resources while guaranteeing nutritional value of the residents.

Impacts of changing cropping pattern on virtual water flows related to crops transfer: a case study for the Hetao irrigation district, China.

BACKGROUND Analysis of cropping patterns is a prerequisite for their optimisation, and evaluation of virtual water 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 sown area of crops increased at an average rate of 3.57 × 10(3) 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 × 10(9) m(3) 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 from the 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.

Actual ET modelling based on the Budyko framework and the sustainability of vegetation water use in the loess plateau

Jointly influenced by the natural factors and the artificial protection measures, the ecological environment of Loess Plateau has been significantly improved in recent years, but which has already brought about some water-related problems. To maintain the balance between precipitation and water consumption is an important foundation for sustainable development of the ecology remediation. This study used Budyko Framework to simulate the actual water consumption of 161 sub-basins from 1990 to 2014. Based on the simulation results, the research also analyzed the evolution characteristics of water balance in Loess Plateau from 1990 to 2014. Results show that, with the increase of vegetation coverage, the regional precipitation and actual evapotranspiration were both showing a significant increasing trend, and the increasing rate of precipitation was 1.91mm/a on average, which was greater than the increasing rate of actual evapotranspiration of 1.34mm/a. To further demonstrate the water balance regime in Loess Plateau, the evapotranspiration coefficient (ECC) was used to quantitatively indicate the ratio of the vegetation water consumption and the total precipitation. The average values of ECC were 0.868, 0.863, 0.851 and 0.837 respectively in four sub-periods of 1990-1999, 2000-2004, 2005-2009 and 2010-2014. The above analyses indicate that with the vegetation recovery and ecological restoration, the percentage of evapotranspiration in the total precipitation is keeping decreasing and in turn the percentage of water yield in the total precipitation is keeping increasing. Consequently, it seems more sustainable for vegetation water use in most areas of Loess Plateau currently.

Impact of Land Use Change on Hydrologic Processes in a Large Plain Irrigation District

Land use is the main factor that influences catchment hydrologic processes, and a better understanding of its effect is important for future land use planning and water resource management. By applying the Soil and Water Assessment Tool (SWAT), we assessed the effects of land use changes on major hydrologic processes (evapotranspiration (ET), discharge, river) on a large plain irrigation district, the Hetao Irrigation District (HID), China. The results indicated that SWAT was a useful tool for simulating the effects of land use changes on regional hydrologic processes. Human activities were the main factors that directly influenced land use in the HID. Land use changes had important impacts on the hydrologic processes of the HID. During 1995–2010, the land use changed greatly in the HID, leading to the changes in ET and discharge. The peak value of ET coincided with the exuberant crop growth period in the maximized sown crop area. In 1995s, wheat maximized the sown area and ET peaked in June; when sunflower and corn maximized the sown area in 2010s, ET peaked in July and August. The increased ET reduced discharge in the same period in the HID. Land use change affected the period and quantity of water diversion in the irrigation district. The quantity of water diverted in 1995 was greater than that in 2010, indicating that land use change significantly impacted the water quantity of the river, which was the water source of the irrigation district. This study will be a reference for future land use planning and water resource management in the irrigation district.