Utilization Efficiency Of Water Resources Research Articles

Study on the Development Path of High Efficiency Water Saving Agriculture in Chengdu Plain under the Background of Rural Revitalization Strategy

In order to effectively promote the overall development goal of Rural Revitalization Strategy, aiming at the problems and development potential of high-efficiency water-saving agriculture in Chengdu Plain, this paper puts forward the conservation tillage technology focusing on Soil and water conservation, the water saving irrigation and rainwater harvesting supplementary irrigation technology focusing on the efficient utilization of water resources, and the chemical irrigation technology focusing on improving the drought resistance ability of crops. The development mode of water-saving agriculture in Chengdu Plain is put forward, which is the combination of water collecting agriculture mode, conservation tillage mode, two season fixed furrow double no tillage mode and modern agricultural water-saving irrigation technology mode. It is not only conducive to food security and regional economic development, but also effectively promote the sustainable development of environmental, ecological and social benefits.

Research on the impact of environmental regulation on water resources utilization efficiency in China based on the SYS-GMM model

Abstract The paper uses the super-efficiency data envelopment analysis (DEA) model to measure the water resources utilization efficiency of 30 provinces in China, and then uses the system generalized method of moments (GMM) model to analyze the impact of environmental regulations on China's regional water resources utilization efficiency. Conclusions as follows. (1) The overall water utilization efficiency is low, and the regions are very unbalanced. The more efficient areas are concentrated in the east, and the less efficient areas are in the west. (2) There is a ‘U’-shaped relationship between the intensity of environmental regulation and water resource utilization efficiency, that is, weaker environmental regulation intensity is not conducive to the improvement of water resource utilization efficiency, but when the intensity of environmental regulation crosses the ‘inflection point’, it can promote the improvement of water resources utilization efficiency. (3) The level of economic development has a very significant positive effect on water resources utilization efficiency, and the coefficient of scientific and technological progress is positive, but the impact of scientific and technological input on water resources utilization efficiency is limited and not significant; industrial structure and water resource utilization efficiency shows a negative correlation; water use structure and water resources efficiency show a negative correlation.

Reference evapotranspiration change in Heilongjiang Province, China from 1951 to 2018: The role of climate change and rice area expansion

It is of great significance to study the variation in reference evapotranspiration (ETo) and the factors that influence it to ensure the sustainable and efficient utilization of water resources. In this study, the spatio-temporal changes in ETo and rice areas as well as the relationship between them in Heilongjiang Province, China, from 1951 to 2018 were analysed by using trend, correlation and contribution analyses. The results showed that rice area expansion is an important factor affecting ETo changes. ETo in Heilongjiang Province decreased during the study period. The areas with high ETo in the Songnen and Sanjiang Plain showed a gradually shrinking trend. Climate change and rice area expansion both contributed to the decline in ETo. The decreases in sunshine duration and average wind speed in Heilongjiang Province were the main reasons for the decrease in ETo. Rice area in Heilongjiang province continued to increase at a rate of 0.54 × 105 ha yr−1. The expansion of rice area in Sanjiang Plain was the largest, followed by Songnen Plain. In response to the rice area expansion, the rise in average temperature slowed down, the average relative humidity was increased, while wind speed was reduced, which directly lead to the decrease in ETo. The effects of the transformation of different land types into rice fields on ETo were different. The cumulative effects of wetlands and dry fields conversion to rice fields on ETo were 7.67 mm yr−1 and − 20.15 mm yr−1 in Sanjiang Plain respectively.

A Novel Approach for the Simulation of Reference Evapotranspiration and Its Partitioning

To estimate the irrigation volume required for agriculture and improve water resources utilization efficiency, it is essential to obtain an estimate of reference evapotranspiration (ET0) and its components (e.g., reference transpiration, T0 and reference soil evaporation, E0). This study updated a soil-plant-atmosphere continuum (SPAC) evapotranspiration model and its associated components to obtain a reference-based SPAC model of reference evapotranspiration (R-SPAC), and it applied the model to an agricultural ecosystem. Model simulations of mean hourly ET0 were benchmarked against those of the Penman-Monteith method by the Food and Agriculture Organization (FAO-PM) throughout the growing season. The resulting good correlation obtained (R2 = 0.96, agreement index, I = 0.98, root-mean-square deviation (RMSD) = 0.05 mm h−1) validated the accuracy of the R-SPAC model. Sensitivity analysis was used to explore uncertainties and errors for ET0, T0, and E0 caused by input variables. The results showed that net radiation and shortwave radiation at the study site were the main drivers of ET0 for both the FAO-PM and R-SPAC models. The study showed that the proposed R-SPAC model can be used for predicting ET0 and for exploring interactions between climate, crop type, and soil in determining evapotranspiration under various future environment conditions.

Compensation benefits allocation and stability evaluation of cascade hydropower stations based on Variation Coefficient-Shapley Value Method

Maximizing the benefits of cascade hydropower stations will inevitably reduce the benefits of some upstream hydropower stations. In order to promote the joint operation and mutual cooperation between cascade hydropower stations, the scientific and fair allocation of compensation benefits between cascade hydropower stations is required. In this paper, a Variation Coefficient-Shapley Value Method for the compensation benefits allocation of multi-owner cascade hydropower stations is proposed, by combining individual characteristic weight coefficients with the Shapley value of each hydropower station. The Propensity to Disrupt (PTD) method is adopted to quantitatively evaluate the stability of the allocation results. Then an exemplary cascade of three hydropower stations on the Nanhe River in China is used as a case to calculate the compensation benefits via the proposed Variation Coefficient-Shapley Value Method and compared with other typical allocation methods. The results show that the leading hydropower station can get more compensation benefits as well as the second and third stage hydropower stations get reasonable compensation benefits. The stability of the cascade alliance in the compensation benefits allocation of the proposed method surpasses that of the other methods. This indicates the ability of the proposed method to both consider the individual marginal contribution and individual characteristics of each hydropower station when participating in joint operation. The proposed method proves to achieve a fair and rational compensation benefits allocation among the cascade hydropower stations and can potentially improve the utilization efficiency of water resources in the river basin.

Optimizing Water Use Structures in Resource-Based Water-Deficient Regions Using Water Resources Input–Output Analysis: A Case Study in Hebei Province, China

Hebei is a representative province facing the scarcity of water resource in China. China is promoting the coordinated development of Beijing, Tianjin, and Hebei, as well as the establishment of Xiong’an New Area. Hebei Province therefore has to bear the population pressure brought by the construction of Xiong’an New Area, while also absorbing the transfer of industries from Beijing and Tianjin. Therefore, its water supply tensions will be further exacerbated. This study constructed an input–output (IO) table utilizing the input and output data of Hebei in 2015 and analyzed the industrial structure and the characteristics of water usage in relevant industries. The research results show that the agricultural sector in Hebei Province consumes the highest water consumption per 10,000 yuan in output value, while the service and transportation industries are the lowest. And a large amount of water used in the agricultural sector is transferred to the manufacturing sector and construction sector in the form of virtual water. The main way to solve the contradiction between water supply and demand in the typical water-deficient areas represented by Hebei Province is to improve water resource utilization efficiency in the short term, and to change the regional water use structure through industrial structure adjustment in the long term.

Calculation of optimal tax rate of water resources and analysis of social welfare based on CGE model: a case study in Hebei Province, China

Abstract The determination of the optimal tax rate of water resources is one of the core as well as the key economic and technological issue in the ‘fee to tax’ work of water resources in China. Therefore, based on the introduction of the computable general equilibrium (CGE) model of water resources tax, using production parameters and consumption parameters of Hebei province in 2008–2017, the optimal tax rate of water resources is simulated and calculated, and the impact of the optimal tax rate on social welfare is analyzed. The results show that the reference of the best water resources tax rate in Hebei Province is 18%, and taxation on water resources effectively promotes the water use structure and water resources utilization efficiency in Hebei, which is beneficial to its water resources protection. The effective calculation of the optimal tax rate of water resources tax in Hebei Province proves the effectiveness of the CGE model in the formulation of water resources tax rate, which provides an important reference for the nationwide popularization of water resources ‘fee to tax reform’ in China and the formulation of water resources tax rate in other regions.

Integrated graphical approach for selecting industrial water conservation projects

Sustainable water management is key to achieving sustainable development goals. Increasing water consumption prompts industrial plants to implement water conservation projects (WCPs) and improve the utilization efficiency of water resources. In this paper, we develop an integrated graphical method for the implementation of water conservation projects by considering both water-saving targets and investment costs with or without government subsidies. First, cost-benefit analysis for different projects is carried out. The unit water saving cost diagram is employed to rank the priority of implementation of each project. Then, the project combination that meets the expected water-saving goal is determined via water-saving pinch analysis. Finally, the water conservation potential and cost-benefit of the optimal project combination are estimated using the marginal cost curve diagram. Two scenarios are considered for the proposed graphical approach: with and without government subsidies. A chlor-alkali/polyvinyl chloride complex is used as an illustrative case study. The results indicate the proposed method can be used to screen out the feasible projects under the constraints of water-saving target and financial fund.

Water use efficiency data from 2000 to 2019 in measuring progress towards SDGs in Central Asia

ABSTRACT Central Asia, located in the hinterland of the Eurasian continent, is characterized with sparse rainfall, frequent droughts and low water use efficiency. Limited water resources have become a key factor restricting the sustainable development of this region. Accurately assessing the efficiency of water resources utilization is the first step to achieve the UN Sustainable Development Goals (SDGs) in Central Asia. However, since the collapse of the Soviet Union, the evaluation of water use efficiency is difficult due to low data availability and poor consistency. To fill this gap, this paper developed a Water Use Efficiency dataset (WUE) based on the Moderate Resolution Imaging Spectroradiometer (MODIS) Gross Primary Production (GPP) data and the MODIS evapotranspiration (ET) data. The WUE dataset ranges from 2000 to 2019 with a spatial resolution of 500 m. The agricultural WUE was then extracted based on the Global map of irrigated areas and MODIS land use map. As a complementary, the water use amount per GDP was estimated for each country. The present dataset could reflect changes in water use efficiency of agriculture and other sectors. The published data are available at http://www.dx.doi.org/10.11922/sciencedb.j00076.00012.

Evaluation of China's water-resource utilization efficiency based on a DEA-Tobit two-stage model

Abstract In this paper, a Data Envelopment Analysis-Tobit (DEA-Tobit) two-stage model was used to evaluate the efficiency of water-resource utilization, and the regional differences and influencing factors on water-resource utilization were analyzed. The results of the analysis of regional differences show that China's water-use efficiency is relatively low. Only Beijing, Shanghai, and Fujian have water-use efficiency higher than 0.8, whereas most other provinces and cities have an efficiency of 0.3–0.8. The eastern region demonstrates a higher water-resource utilization efficiency than the central and western regions. The analysis of the influencing factors of regional differences in water-use efficiency found that per capita water resources, per capita domestic water use, and the proportion of primary and secondary industries all have a negative impact on the efficiency of water use, and per capita GDP has a positive impact on the efficiency of water use. Agricultural water consumption, industrial water consumption, domestic water consumption, and total ecological water consumption all have a negative impact on water-resource utilization efficiency, of which domestic water consumption and industrial water consumption have a greater impact. Technological level and water-resource utilization efficiency show a significant positive correlation.

Assessment of rain-flood availability in the upper reaches of Hanjiang River and its water-constrained response

In order to analyze the potential of rain-flood resources, and to reveal its water-constrained response to further develop the assessment method of rain-flood availability, based on the conceptual model, this paper takes the upper reaches of Hanjiang River (UHRB) as a demonstration area to carry out the assessment of rain-flood availability. According to the constraint factors, analysis of water-constrained response has been conducted. It is found that the average annual rain-flood availability amount during the flood season in UHRB is 17.30 billion m3, and the rain-flood utilization potential is 5.37 billion m3, showing a decreasing trend since the 21st century. Rain-flood utilization is directly constrained by regulation ability and necessary water requirements such as production, living and ecological environment, and there is an obvious non-linear response relationship. Based on scenario assumptions, the iso-curve of rain-flood resources availability and utilization potential that meet the practical needs of water resources utilization could be drawn. The findings enrich the evaluation theory of rain-flood resources and provide technical support for improving the water resources utilization efficiency.

Measurement and Influencing Factors of Industrial Water Resource Utilization Efficiency in Yangtze River Economic Belt

The governance of industrial water environment in the Yangtze River Economic Belt (YREB), the demonstration zone of ecological civilization in China, has attracted a growing attention. In this paper, an evaluation index system (EIS) with undesired output is established for industrial water resource utilization efficiency (IWRUE). Next, the stochastic block model (SBM) was adopted to measure the IWRUEs of the 11 YREB provinces in 2003-2017. After that, the Tobit model was employed to examine the influencing factors of the IWRUE. The results show that the YREB provinces differed sharply in IWRUE through the sample period; the downstream provinces achieved relatively satisfactorily IWRUEs, while most provinces in the upstream and midstream performed unsatisfactorily. The downstream of the YREB realized the highest IWRUE, followed in turn by the upstream, and the midstream. The YREB is significantly promoted by economic development, ownership structure, and opening-up, and significantly suppressed by water endowment, technological progress, and government influence.

Decoupling analysis of water use and economic development in arid region of China – Based on quantity and quality of water use

Decoupling water use from economic development is a fundamental strategy to improve environmental quality from the source. It can promote economic growth while reducing water use and water pollution. This article uses water footprint theory to calculate the relevant indicators of the water quantity footprint and water quality footprint of the Northwest arid region between 1997 and 2017. This paper not only comprehensively consider the impact rate of economic development on water resource consumption and water pollution, but also analyzes the coordination of water resource utilization efficiency and economic development from the perspective of water resource flow, and make up for the deficiencies of pure consideration of water resource consumption. The results of the study show that in the past 20 years, the water resources utilization and economic development in Northwest arid region of China has shown relatively decoupling and weak negative decoupling, and the decoupling index of water quantity and water quality with economic development are 0.3377 and 0.3156, respectively. It shows that the dependence of economic development on water resources is gradually decreasing. However, the water shortage remains serious, this also shows that the efficiency of water use has not improved. Only if economic development is decoupled from water quantity and water quality at the same time, we can achieve sustainable development of water use and economy. We also found that the proportion of agricultural production water is too large, industrial water consumption is declining, and the proportion of domestic water consumption is increasing. There is a problem of unreasonable utilization structure and it can be seen from the wastewater discharge data that the discharge of industrial wastewater is declining. The government needs to focus on the wastewater treatment, strengthen the awareness regarding of water conservation at same time, and use stepped pricing standards to reasonably control water use.

Optimal allocation of regional water resources based on multi-objective dynamic equilibrium strategy

Raising water demand, insufficient freshwater resources and uneven precipitation are the main causes of water conflicts in the river basin. The main challenges in water resources allocation are the following: first, the uncertainty of water supply caused by climate change; second, the dynamic allocation of water resources is not considered; third, there is a lack of equitable water allocation, which may lead to intensified conflicts among the water user sectors. Based on the above challenges, a multi-objective dynamic programming optimal water resources allocation model under uncertainties is established in this paper, which could be a resolution for water disputes as it addresses simultaneously economic, social and environmental benefits. The proposed model considers maximizing the minimum satisfaction degree of each water sector, maximizing the utilization efficiency of water resources in the basin, and maximizing economic benefits. Satisfaction degree function is introduced to optimize water allocation equality in water use sectors (agricultural, domestic, and industrial sectors), and economic efficiency loss acceptance is integrated into the model constraints to control the economic loss corresponding to variations in water availability. In addition, a case study demonstrated the practicality and rationality of the proposed model, and the model results proposed herein show significantly help for a single river basin. Most importantly, the results show that model with dynamic constraint ensures a greater overall economic return for the entire basin, and a larger variation in water resources of sub-area leads to a larger maximum economic efficiency loss. Moreover, the proposed model herein is flexible and can be used in other developing countries/regions only by modifying the parameters according to the actual situation.

Evaluating the effectiveness of the water-saving society construction in China: A quasi-natural experiment

The conservation and efficient use of water resources are directly related to the sustainable and high-quality development in China. This paper regards the pilot policy of water-saving society construction as a quasi-natural experiment, and employs a differences-in-differences approach to evaluate the effectiveness of urban water-saving policies and exploit its drive mechanism by using the panel data of 263 cities in China from 2001 to 2016. Findings show that the pilot policy of water-saving society construction can achieve better water-saving effects, which can not only promote the reduction of urban water consumption in intensity and total amount, but also improve the efficiency of water resources utilization. And this policy has brought long-term dynamic effects on the urban water resources conservation. Heterogeneous effects exist in different types of cities, that is, the water-saving performance is more significant in cities with sufficient water resources and in central China. Besides, this paper finds that the impact of this water-saving policy on urban water resource conservation is mainly through two channels such as water resources infrastructure investment and water resources pricing. These findings provide useful inspirations for local governments to take effective economic measures to manage water resources.

Study on the spatial-temporal variation in evapotranspiration in China from 1948 to 2018

It is of great significance for the efficient utilization of water resources and the construction of the ecological environment in China to fully understand the evolution process of the spatial-temporal pattern of evapotranspiration (ET). With the use of the v2.0 and v2.1 ET data sets combined with the Global Land Data Assimilation System and Noah model, this paper selects pixels as the basic research object to analyse the spatial-temporal variation in ET in China during the 71 years from 1948 to 2018. We first applied the TFPW-MK test to study the annual ET trend in China throughout the 71-year period, including the ET trend of each month from January to December and the annual total ET trend. Moreover, we examined the spatial variation in these trends. In addition, we calculated the variation coefficient of the time series of each pixel’s ET throughout the 71-year period and the variation coefficient of the spatial distribution of ET in each year to analyse the spatial-temporal fluctuations in ET in the study area. Finally, the Hurst index was adopted to evaluate the future ET trend. Based on these analyses, we observed the following novel spatial-temporal characteristics of ET: from 1948 to 2018, (1) the ET in most regions covered by 89.5% of all pixels in China exhibits an increasing trend. (2) The ET trend in China varies greatly with the change in months, and many regions show the most or least obvious increasing trend (or decreasing trend) at different times. (3) The area with an increasing trend is the largest in May and the smallest in December, and more than half of the pixels in all months of a year reveal an increasing trend. (4) In the northeast, west and south regions of China, the monthly fluctuation in the ET trend is relatively large, which indicates that the ET trend in these regions is greatly affected by the month. (5) The fluctuation in ET in China is larger in the north than it is in the south and larger in the west than it is in the east. The most stable fluctuation occurs in East China. (6) The ET trend of almost all the pixels in the study area remains consistent from 1948 to 2018, and there are large areas with a notable continuity. This results in the spatial variation in ET in the study area increasing.

Economic Benefit Evaluation of Water Resources Recycling Utilization based on Analytic Hierarchy Process

Wu, X., 2020. Economic benefit evaluation of water resources recycling utilization based on analytic hierarchy process. In: Guido Aldana, P.A. and Kantamaneni, K. (eds.), Advances in Water Resources, Coastal Management, and Marine Science Technology. Journal of Coastal Research, Special Issue No. 104, pp. 6–9. Coconut Creek (Florida), ISSN 0749-0208.Due to the backwardness of current industrial production mode and technology and people's lack of understanding of water crisis and other reasons, there are low utilization efficiency and serious waste in the process of using water resources, which aggravates the shortage of water resources. In order to improve the utilization rate of water resources and improve the economic benefits of water resources, an evaluation method of economic benefits of water resources recycling based on analytic hierarchy process (AHP) is proposed. This paper introduces the theoretical basis of the development of circular economy, analyzes various modes of the development of circular economy of urban water resources, and forecasts the optimal water demand quota or water demand of a certain region in a certain period through the elastic coefficient method of water price. On this basis, the hierarchical structure model is established by using the multi index system of regional water resources recycling, and the directional distance function model is constructed to measure the water resources utilization efficiency reasonably. Finally, the index weight and comprehensive correlation degree are determined based on the analytic hierarchy process to realize the evaluation of economic benefits of water resources recycling. Based on the basic data of water resources utilization in a certain region from 2015 to 2019, this paper evaluates the benefits of water resources recycling utilization, and concludes that the economic development level has a significant positive effect on the water resources utilization efficiency, and the industrial water use efficiency is the main factor determining the water resources utilization efficiency. According to the results, it provides reference for the utilization of water resources.

Identification of EDI trend using Mann-Kendall and Şen-Innovative Trend methods (Uttarakhand, India)

Under the climate change scenario, the identification of drought trends is primarily essential for the efficient utilization of water resources. In this paper, two methods, including traditional Mann-Kendall (MK) and graphical Şen-Innovative Trend (ŞIT), were utilized for Effective Drought Index (EDI) trend detection at 13 meteorological stations situated in the State of Uttarakhand, India. The EDI was computed for 54 years from 1962 to 2015 using monthly rainfall data at the study stations. The magnitude (mm/year) of the EDI was derived by Sen’s-Slope Estimator (SSE) method. In total, 156 series of data were analyzed, and the results showed that the ŞIT method detected a significantly negative/positive trend in 71/60 time series, while the MK method detected a significantly negative/positive trend in 25/9 time series from January to December at the study stations. Magnitude (mm/year) varies from − 0.0275 to 0.0256 (January), − 0.0352 to 0.0343 (February), − 0.0312 to 0.0312 (March), − 0.0343 to 0.0276 (April), − 0.0359 to 0.0237 (May), − 0.0293 to 0.0205 (June), − 0.0234 to 0.0235 (July), − 0.0277 to 0.0405 (August), − 0.0297 to 0.0247 (September), − 0.0288 to 0.0227 (October), − 0.0290 to 0.0241 (November), and − 0.0298 to 0.0236 (December) over the study region. Additionally, the results indicated the supremacy of the ŞIT method by examining the unobserved trend that cannot be detected by the MK method over the study region in the EDI data series. In general, the EDI trend was found negative (decreasing) and positive (increasing), which suggested that more attention should be paid towards drought and wet (i.e., moderate, severe, extreme) at the study stations. The results of this research can be employed for water resource management and understanding the characteristics of climate variation over the study area.

Evaluation of Water Resources Utilization Effectiveness Based on Eco-economics Theory

Chen, Y.; Li, Z.; Li, P.; Gao, H.; Jin, T.; Du, P., and Zhang, Y., 2020. Evaluation of water resources utilization effectiveness based on eco-economics theory. In: Bai, X. and Zhou, H. (eds.), Advances in Water Resources, Environmental Protection, and Sustainable Development. Journal of Coastal Research, Special Issue No. 115, pp. 148-150. Coconut Creek (Florida), ISSN 0749-0208.Facing the increasingly severe water resources situation, how to manage water resources reasonably and effectively, and improve the utilization efficiency and efficiency of water resources is an inevitable requirement for the overall development of China's economic and social water resources ecological environment system. Based on this, the effect of water resources utilization is evaluated based on the theory of ecological economics. The SVM correlation model algorithm is proposed. The dynamic analysis and simulation evaluation are carried out through SD simulation technology, and the total system flow diagram of regional water resources utilization evaluation is established. Based on the maximum flow algorithm, the incentive degree of water resources ecological compensation mechanism is studied. InVEST model and household survey are used to calculate the new water conservation and land use conversion costs. After considering the risk of water resources ecosystem loss, the welfare cost method is adopted. On the county scale, the potential objects of ecological compensation for water resources in the Weihe River Basin are identified. The results show that there are obvious spatial differences in water resources ecological compensation efficiency coefficients in Gansu section of Weihe River Basin. Weiyuan County with the highest runoff is 1.26, Gangu County with the lowest runoff is 0.46. The efficiency of the project can be increased by 40.54% after spatial screening of regional compensation objects. Through the evaluation of water resources utilization and water resources policy simulation, it provides a reference for the coordinated development of water resources and social economy in China.

A validation of eddy covariance technique for measuring crop evapotranspiration on different time scales in the North China Plain

Accurate determination of evapotranspiration (ET) has tremendous potential in guiding irrigation and improving the efficiency of water resources utilization in the North China Plain. Eddy covariance (EC) method is currently a popular method for determining field-scale ET. However, due to varying foot print and unclosed energy balance, the applicability of EC in different regions needs to be tested and corrected. In present work, we compared the ET of the winter wheat – summer maize rotation cropland measured by the EC method with the ET measured by large-scale lysimeters on different time scales. The degree of energy balance closure of EC measurements in this region is 78%. After adjusted by using Bowen ratio forced closure method, the ET monitored by EC is comparable with those monitored by large-scale lysimeters. The results also indicated that the consistency of the observed ET by the EC and lysimeters got better with an increasing time scale, especially for the multi-year average ET values with a relative deviation of less than 1%. The short-time events such as irrigation and precipitation and the mismatch of the varying footprint area of the EC and the small fixed source area of the lysimeter should be responsible for the discrepancy of ET in two methods on daily scale. However, the factors of crop biomass, total available water, and local climate condition exert more effects on the observed ET on large time scale. Overall, the EC technique is responsible for ET measurement of winter wheat – summer maize rotation cropland of the North China Plain.