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The irrigation water effective utilization coefficient (IWEUC) is a critical indication of agricultural water use efficiency. To improve water-saving potential, the inter-annual variation of IWEUC from 2014 to 2021 in Jiangsu Province was analyzed. Taking consideration of natural factors, planting structure, management levels, and water-saving engineering, the primary influencing factors of IWEUC were investigated through principal component analysis. The results revealed that IWEUC in Jiangsu Province was higher than the annual national level and showed an insignificant increasing trend. IWEUC and its trend were negatively correlated with irrigation district size. Water-saving irrigation areas had an extremely significant impact on IWEUC (P < 0.01). The positive load of water-saving engineering investment was rated first. Furthermore, economic and water-saving benefits for different irrigation district scales based on the TOPSIS model were evaluated. Despite restricted government support, the economic gains for large irrigation districts were superior to those for small irrigation districts. In the past decade, agricultural water declined while agricultural water conservation rose. The completion of integrated agricultural water pricing reform, as well as the improvement of water-saving engineering and optimization of management level, had a significant beneficial influence on IWEUC. Jiangsu's IWEUC has been efficiently implemented, and provides guidelines in other regions.

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  • The inter-annual fluctuation of irrigation water effective utilization coefficient in Jiangsu Province in recent years is comprehensively introduced.

  • Dominant factors affecting irrigation water effective utilization coefficient through principal component analysis are analyzed.

  • Economic and water-saving benefits for different irrigation district scales based on the TOPSIS model are evaluated.

integrated agricultural water pricing reform, irrigation water use efficiency, Jiangsu Province, PCA, TOPSIS, water-saving irrigation
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With the drastic increasing water demand in the past decades, water has been an essential economic and strategic resource that threatens sustainable development. Governments around the world are facing the challenge of water scarcity and agricultural production (Shu et al. 2021). China is a country with abundant total water resources, while the per capita water resources are only one-third of the world's average. The demand for water resources is increasing with industrial and agricultural development (Fei et al. 2021). China is an agricultural development country and agricultural water makes for a significant amount of overall water usage, with over 95% of it being utilized for irrigation (Han et al. 2020). According to predictions, China's farmland area would reach 100 billion m2 by 2050, and the annual agricultural water scarcity will reach 3 × 1010 m3 (Hamdy et al. 2003; Yang et al. 2021). The demand for agricultural irrigation water will continue to rise, posing a greater challenge to sustainable agricultural growth (Wang et al. 2015). Due to inefficient agricultural water use, the irrigation water effective utilization coefficient of China in 2020 was 0.565, lower than the level of 0.7–0.8 in developed nations, indicating a significant difference (Song et al. 2018b; Shi et al. 2022). As a result, the potential for improving China's irrigation water effective utilization coefficient is enormous. The key to long-term agricultural growth is increasing irrigation water efficiency, which is a crucial prerequisite for water conservation and emission reduction, reducing existing agricultural water pressure, avoiding food crises, and so on (Tang et al. 2015; Liu et al. 2019; Mbava et al. 2020).

Research on irrigation water effective utilization coefficient has been ongoing. The phrase ‘utilization coefficient of irrigation water’ was initially introduced as the ratio of the amount of irrigation water absorbed by crops growing under the control of the irrigation project to the water diverted from a river or a well (Israelson & Hansen 1963). In 1977, the International Organization of Irrigation and Drainage (ICID) defined it as the ratio of the crop water requirement to the total water flowing into the canal water system (Bos 1979). In 2006, the Ministry of Water Resources of the People's Republic of China defined it specifically as the ratio of net irrigation water used by crops to total irrigation used at the head of water source (Guo et al. 2019a). It has been widely used in China as one of the primary evaluation indicators for irrigation potential and efficiency. Currently, the most common method for measuring the irrigation water effective utilization coefficient is ‘the head and end measurement’, which has reduced the limitations of the traditional multiplication coefficient method, and provides an efficient way to conduct the work on irrigation water effective utilization coefficient research (Wang et al. 2012; Feng et al. 2020). To calculate the irrigation water effective utilization coefficient, domestic and foreign scholars have used the remote sensing model (Ahadi et al. 2013), geographically weighted regression model (Tromboni et al. 2014; Shi et al. 2022), and deterministic and stochastic models (Pereira & Marques 2017). The findings revealed that the irrigation water effective utilization coefficient of China has risen, with a higher coefficient in the northwest (Feng et al. 2020). Multiple factors influence the irrigation water effective utilization coefficient, e.g. agricultural irrigation technologies (Grashey-Jansen 2014), water prices (Hussain et al. 2007), socio-economic development level (GDP) (Liu et al. 2013), scales of irrigation areas and channel levels (Jia et al. 2008), level of water management (Li et al. 2019), etc.

China has the largest drip irrigation area under agricultural mulch (Song et al. 2018a), with significant potential for irrigation water use efficiency. To relieve agricultural water stress, in 2012, the central government proposed ‘Views on the Implementation of the Most Stringent Water Resources Management System’ (State Council Document No. 3, 2012), stating that ‘by 2020, the irrigation water effective utilization coefficient should increase to over 0.55″. In 2013, the State Council released ‘Assessment on Implementation of the Most Stringent Water Resources Management System’, which clearly stated each province's responsibility to carry out the policy and defined the irrigation water effective utilization coefficient as an assessment indicator. In recent years, Jiangsu Province, as a developed province in China, has led the country in terms of irrigation water effective utilization coefficient thanks to the water-saving reconstruction of large and medium-sized irrigation districts, high standard farmland construction, new million kilos of grain field project, integrated agricultural water pricing reform, and other initiatives (Shang et al. 2019; Yang et al. 2022a).

In general, most studies are based on qualitative analysis because most influencing factor data are difficult to obtain. However, research on quantitative analysis of influencing factors and benefits on the irrigation water effective utilization coefficient is lacking, and the majority of studies focused on policy discussions (Yang et al. 2022b) and management methods (Wang et al. 2022) in Jiangsu Province, researches on the inter-annual variation of irrigation water effective utilization coefficient, analysis of main influencing factors, and its benefits through statistical models are sparse. Taking Jiangsu as an example, the following goals were sought after by this work, which utilized the principal component analysis (PCA) method and technique for order preference by similarity to ideal solution (TOPSIS) model: i) analyze the inter-annual variation of irrigation water effective utilization coefficient in recent years from multidimensional perspectives; ii) determine the dominant factors affecting irrigation water effective utilization coefficient from the perspective of natural factors, planting structure, management factors, and water-saving projects; iii) evaluate the economic, water-saving, and policy benefits of engineering investment in irrigation districts of different sizes, in order to give references for enhancing Jiangsu's or other Chinese provinces' irrigation water efficiency, as well as fundamental information for updating water-saving or master plans in national irrigation areas during the 14th Five-Year plan as well (Robinson 2015; Chaudhry 2018).

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Location and irrigation districts of Jiangsu

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Jiangsu has a total size of 107,200 km2 and is situated on the eastern coast of China, between 116°18′–121°57′E, 30°45′–35°20′N (Figure 1). Jiangsu has a total cultivated area of 543.02 million hm2, making it one of the top agricultural producers in China. The grain yield in 2021 was 37.46 billion kg, placing it third among the major grain-producing provinces and eighth overall in the nation (Jiangsu Bureau of Statistics 2021). Grain yield is mostly produced in large- and medium-sized irrigation districts, which account for more than 70% of the overall output. As a result, the vital basis for food security is large- and medium-sized irrigation areas. The central and northern regions of Jiangsu are dominated by large- and medium-sized irrigation districts, whereas the southern region has small-sized irrigation districts (Figure 1). By the end of 2021, there were 34 large-sized irrigation districts and 264 medium-sized irrigation districts in Jiangsu, covering a total effective irrigated area of 274.98 million hm2. The province has 14,862 minor irrigation districts, with a total effective irrigation area of 148.33 million hm2.
Figure 1
Distribution of large- and medium-sized irrigation districts in Jiangsu Province.
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Distribution of large- and medium-sized irrigation districts in Jiangsu Province.

Figure 1
Distribution of large- and medium-sized irrigation districts in Jiangsu Province.
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Distribution of large- and medium-sized irrigation districts in Jiangsu Province.

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Agricultural irrigation water demand in Jiangsu

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Jiangsu has 15 irrigation quota subregions with rice being the most irrigated crop (Figure 2). The irrigation quota for rice (including additional water quota) is 495–640 m3/667 m2 in the median water year and 560–695 m3/667 m2 in the dry year (Jiangsu Provincial Department of Water Resources 2019). Based on planting structure and irrigation quota, the agricultural irrigation water demand was 20.78–25.53 billion m3 in the median water year and 24.45–28.87 billion m3 in the dry year. According to measured data, the actual gross irrigation water in small-, medium-, and large-sized irrigation districts was 26.81 billion m3 in 2019. Precipitation in general years can meet the water demand for crops, but 2019 was a dry year, necessitating the dispatch of transit water to guarantee agricultural water demand.
Figure 2
Irrigation quota subregions in Jiangsu.
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Irrigation quota subregions in Jiangsu.

Figure 2
Irrigation quota subregions in Jiangsu.
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Irrigation quota subregions in Jiangsu.

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Water supply capacity of Jiangsu

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The annual total water consumption (ATWC) in Jiangsu was 45.27–49.34 billion m3 and the average annual water consumption was 46.67 billion m3, according to an analysis of the use of water resources from 2014 to 2020 (Table 1). The primary industry consumed an average of 28.15 billion m3 of water per year, ranging from 26.66 to 30.31 billion m3. Among them, the annual average agricultural irrigation water consumption was 24.70 billion m3, accounting for 52.9% of the ATWC. The average water consumption in the secondary and tertiary industries was 12.61 and 1.71 billion m3, accounting for 27.1 and 3.7% of the ATWC, respectively.

Table 1

Annual water consumption in Jiangsu from 2014 to 2020 (unit: 100 million m3)

YearATWCPrimary industry
Secondary industryTertiary industryDomesticOther
ConsumptionAgricultural irrigation (AI)Proportion of AI in ATWC (%)
2014 480.7 297.8 259.5 54 129.5 14.9 35.8 2.7 
2015 460.6 279.1 242.8 52.7 127.3 15.6 36.6 2 
2016 453.2 270.1 237.2 52.3 126.6 16.3 37.5 2 
2017 465.9 280.6 247.8 53.2 127 17.5 38.7 2.1 
2018 460.2 273.4 233.2 50.7 125.8 19.3 39.2 2.5 
2019 493.4 303.1 268.1 54.3 125.4 20.5 40.6 3.8 
2020 452.7 266.6 240.3 53.1 121.2 15.8 44.3 4.8 
Average 466.7 281.5 247.0 52.9 126.1 17.1 39.0 2.8 
YearATWCPrimary industry
Secondary industryTertiary industryDomesticOther
ConsumptionAgricultural irrigation (AI)Proportion of AI in ATWC (%)
2014 480.7 297.8 259.5 54 129.5 14.9 35.8 2.7 
2015 460.6 279.1 242.8 52.7 127.3 15.6 36.6 2 
2016 453.2 270.1 237.2 52.3 126.6 16.3 37.5 2 
2017 465.9 280.6 247.8 53.2 127 17.5 38.7 2.1 
2018 460.2 273.4 233.2 50.7 125.8 19.3 39.2 2.5 
2019 493.4 303.1 268.1 54.3 125.4 20.5 40.6 3.8 
2020 452.7 266.6 240.3 53.1 121.2 15.8 44.3 4.8 
Average 466.7 281.5 247.0 52.9 126.1 17.1 39.0 2.8 
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Local water resources and transit water resources are among Jiangsu's water resources. Over the years, the annual average local water resources have been 32.70 billion m3. The average transit water volume from the Yangtze River is 1025.4 billion m3, accounting for about 95% of total transit water volume. Jiangsu has a large agricultural irrigation water demand, yet the local water resources are limited, and water scarcity problems occurred in 60% of the statistical years (Figure 3). The worst water deficit occurred in 2019, totaling 26.17 billion m3, while the smallest occurred in 2017, totaling 7.3 billion m3. Because agricultural irrigation water cannot be adequately assured by depending solely on local water supplies, it is critical to improving irrigation water efficiency.
Figure 3
Annual water shortage in Jiangsu Province (relative to local water resources).
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Annual water shortage in Jiangsu Province (relative to local water resources).

Figure 3
Annual water shortage in Jiangsu Province (relative to local water resources).
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Annual water shortage in Jiangsu Province (relative to local water resources).

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This study used the principal component analysis (PCA) method and technique for order preference by similarity to ideal solution (TOPSIS) model to accomplish the following goals (Figure 4): i) examine the inter-annual variation of irrigation water effective utilization coefficient in recent years from multidimensional perspectives; ii) identify the dominant factors influencing irrigation water effective utilization coefficient from the perspective of natural factors, planting structure, management factors, and water-saving projects; iii) evaluate the economic benefits of engineering investment in irrigation districts of different sizes, and assess the water-saving and policy benefits in recent years.
Figure 4
Flowchart of the study.
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Flowchart of the study.

Figure 4
Flowchart of the study.
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Flowchart of the study.

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Irrigation water effective utilization coefficient

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In China, the ‘head and end’ measurement was used to compute the irrigation water effective utilization coefficient (IWEUC) in the sample irrigation districts (Jia & Zheng 2013; Feng et al. 2020). This method was based on the real state of Jiangsu to measure the net irrigation water consumption and gross irrigation water consumption (Li et al. 2018; Yang et al. 2021). The specific calculation process is shown in Figure 5.
  • (i)

    Select sample irrigation districts. The topography, soil structure, engineering facilities, planting structures, irrigation areas, and other factors were considered, and 225 sample irrigation districts were chosen in Jiangsu by 2021, including 34 large-scale sample irrigation districts, 41 medium-scale sample irrigation districts, and 150 small-scale sample irrigation districts in accordance with the principles of representativeness, feasibility, and stability.

  • (ii)

    IWEUC of sample irrigation districts. Firstly, we chose typical fields with obvious boundaries, regular shapes, and reasonable areas. A total of 1141 typical fields were chosen in Jiangsu by 2021, including 414 typical fields in large-scale sample irrigation districts, 348 typical fields in medium-scale sample irrigation districts, and 379 typical fields in small-scale sample irrigation districts. The observed crop species are mainly rice. Secondly, the average net irrigation water consumption of a typical field was measured as shown in Figure 6. The direct measurement method is preferred, and observation analysis can used for those which do not have actual measurement conditions.

Figure 5
Calculation framework of irrigation water effective utilization coefficient.
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Calculation framework of irrigation water effective utilization coefficient.

Figure 5
Calculation framework of irrigation water effective utilization coefficient.
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Calculation framework of irrigation water effective utilization coefficient.

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Figure 6
Calculation of annual average net irrigation water consumption per acre in a typical field.
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Calculation of annual average net irrigation water consumption per acre in a typical field.

Figure 6
Calculation of annual average net irrigation water consumption per acre in a typical field.
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Calculation of annual average net irrigation water consumption per acre in a typical field.

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In this paper, we use a direct measurement method to assess net irrigation water consumption in typical years (Figure 7(b)). If there is water in the field before irrigation, we choose water level observation wells (Figure 7(a)), which measure the change of field surface water depth before and after each irrigation. The formula is as follows:
(1)
where is the average net irrigation water consumption per acre in a typical field, m3/hm2; is the water level before irrigation, mm; is the water level after irrigation, mm.
Figure 7
(a) Water level observation well diagram; (b) Field test of sample irrigation districts.
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(a) Water level observation well diagram; (b) Field test of sample irrigation districts.

Figure 7
(a) Water level observation well diagram; (b) Field test of sample irrigation districts.
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(a) Water level observation well diagram; (b) Field test of sample irrigation districts.

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If there is no water in the field before irrigation, we measure in two parts, one part is the change of soil volumetric water content before it reaches saturation. The formula is as follows:
(2)
where is net irrigation water of non-aquic field irrigated until soil is saturated, m3/hm2; is scheming wetted soil layer depth, mm; is the volumetric water content of soil saturation, %; is the initial soil volumetric water content, %.

Another part is the amount of irrigation water after the soil is saturated. The sum of the two parts is the average net irrigation water consumption of typical field. The total net irrigation water consumption in a typical field can be obtained by adding up the average net irrigation water consumption for each irrigation.

Then, calculate annual net irrigation water consumption in sample irrigation districts. The formula is as follows:
(3)
where is the annual net irrigation water consumption in sample irrigation districts, m3; is the net irrigation water consumption in a typical field, m3/hm2; is the irrigation area of typical field, hm2; is the irrigation area of sample irrigation districts, hm2.
Thirdly, the gross irrigation water consumption is determined by actual measurement, e.g. current meter. Finally, the IWEUC of the sample irrigation districts was estimated based on the annual net irrigation water consumption and gross irrigation water consumption. The following is the formula:
(4)
where is the IWEUC of sample irrigation district; is the net irrigation water consumption of sample irrigation districts, m3; is the gross irrigation water consumption of sample irrigation districts, m3.
  • (iii) IWEUC of provincial region. The provincial regional IWEUC of large- and medium-sized irrigation districts were determined using the IWEUC of the sample irrigation districts and irrigation water consumption through the weighted average method, respectively, while provincial regional IWEUC of large-sized irrigation districts were based on arithmetic mean method. Finally, the IWEUC of Jiangsu was calculated:
    (5)
    where ⁠, ⁠, are the IWEUC of large-, medium- and small-sized irrigation districts; ⁠, ⁠, are the gross irrigation water consumption of large-, medium- and small-sized irrigation districts, m3.

  • (iv) Reasonableness test. In the calculation process, the water administrative department should analyze the rationality of the IWEUC of the sample irrigation area, and audit the final results to ensure the reliability of the results.

Principal component analysis

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In order to select the influencing factors comprehensively and objectively, the following nine influencing factors were selected for quantitative analysis, taking into account the natural factors, planting structure, management factors, and water-saving engineering (Table 2). An index system of influencing factors was established.

Table 2

Index system of influencing factors

TypeInfluencing factorsVariablesUnitData sources
Natural factors Precipitation X1 mm Jiangsu Water Resources Bulletin 
Evapotranspiration X2 mm 
Planting structure Rice planting ratio X3 % Jiangsu Statistical Yearbook 
Weighting irrigation quota X4 m3/hm2 Jiangsu Irrigation Water Quota 
Management factors Actual irrigated area X5 million hm2 Statistical data of irrigation districts 
Average gross irrigation water X6 m3/hm2 
Water-saving engineering Water-saving irrigation area X7 million hm2 
Water-saving irrigation engineering investment X8 million yuan 
Channel lining rate X9 % 
TypeInfluencing factorsVariablesUnitData sources
Natural factors Precipitation X1 mm Jiangsu Water Resources Bulletin 
Evapotranspiration X2 mm 
Planting structure Rice planting ratio X3 % Jiangsu Statistical Yearbook 
Weighting irrigation quota X4 m3/hm2 Jiangsu Irrigation Water Quota 
Management factors Actual irrigated area X5 million hm2 Statistical data of irrigation districts 
Average gross irrigation water X6 m3/hm2 
Water-saving engineering Water-saving irrigation area X7 million hm2 
Water-saving irrigation engineering investment X8 million yuan 
Channel lining rate X9 % 
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Since the indicators selected in this paper were complicated and overlap in the information, the Principal Component Analysis (PCA) method was chosen to recombine multiple variables into several primary comprehensive indicators using a dimension-reduced processing method (Liu & Chang 2008; Abegaz et al. 2018; Liu et al. 2020). In general, the principal components with eigenvalues greater than 1 and a cumulative contribution rate of more than 80% present the key aspects of the original data, which may be important influencing elements for IWEUC.

Technique for order preference by similarity to an ideal solution

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The distance between the most inferior (superior) solution and the evaluation object was sufficiently used by TOPSIS (Technique for Order Preference by Similarity to an Ideal Solution) to determine the final ranking after taking into account the proximity between the ideal target and the assessment object, so that the assessment object's superiority or inferiority may be assessed more sensibly. The TOPSIS has been extensively employed in the evaluation of irrigation water use efficiency (Huang & Qu 2021), the performance of drainage networks (Aghajani et al. 2017), and the influence of water-saving on rice quality (Zheng et al. 2017), etc. There are four most prevalent forms of indicators, extremely large indicators, extremely small indicators, intermediate indicators, and interval indicators. We may construct a judgment matrix (Z) based on the characteristics of each indication and determine the relative proximity of each target (S). Ultimately, the relevant assessment objectives were sorted in descending order of S. The target is better if the S value is greater. In the reference, a specific computational method was illustrated (Chen 2019).

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Annual trend analysis of IWEUC

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In the past decade, the construction of auxiliary facilities and water-saving modifications for irrigation districts along with the release of ‘the Most Stringent Water Resources Management System’ by the Ministry of Water Resources of the People's Republic of China, have improved the engineering conditions and the management level of irrigation districts. As a result, the IWEUC has gradually improved in China and Jiangsu (Figure 8). In 2020, the national IWEUC reached 0.565, with an increase of 10.78% from 2011, and the IWEUC of Jiangsu reached 0.616, with an increase of 8.64%. The IWEUC and regional economic growth are somewhat related. As a developed province, the IWEUC was higher than the annual national level of 9–11.6% in Jiangsu. The findings of (Liu et al. 2013) can verify our point of view.
Figure 8
IWEUC and its increasing trend of China and Jiangsu.
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IWEUC and its increasing trend of China and Jiangsu.

Figure 8
IWEUC and its increasing trend of China and Jiangsu.
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IWEUC and its increasing trend of China and Jiangsu.

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Jiangsu's irrigation districts are intricate, with a wide range of engineering and administration styles, which contributes to IWEUC's poor accuracy. In order to strengthen the construction of metering facilities for rural water conservancy projects, the Jiangsu Provincial Department of Water Resources promulgated the ‘Notice on Strengthening the Construction of Metering Facilities for Rural Water Conservancy Projects’ in 2015. This notice placed a focus on metering facility management and construction from 2016. IWEUC in Jiangsu rose, as shown in Figure 9, but the pace of growth has been steadily slowing since 2016. As a consequence, the rate of growth was greater during the preliminary planning period than that during the mid-term and post-consolidation periods. With the completion of integrated agricultural water pricing reform in the post-consolidation period, the level of agricultural irrigation water metering facilities increased with steady growth. Based on the change of coverage rate of measurement facilities in the integrated agricultural water pricing reform, this paper further analyzed the causes of the slow growth of effective utilization coefficient of irrigation water, which is a supplement to the previous results.
Figure 9
Comparison between construction progress of metering coverage rate and increasing rate of IWEUC.
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Comparison between construction progress of metering coverage rate and increasing rate of IWEUC.

Figure 9
Comparison between construction progress of metering coverage rate and increasing rate of IWEUC.
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Comparison between construction progress of metering coverage rate and increasing rate of IWEUC.

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Based on the water source, we separated the irrigation districts in this study into lift irrigation districts and self-flow irrigation districts (Figure 10). Results showed that the IWEUC was found to be negatively correlated with the size of the irrigation district (⁠⁠), and the IWEUC of lift irrigation districts was higher than that of self-flow irrigation districts. Due to the smaller area and more challenging management, the IWEUC of small- and medium-sized irrigation districts rose more swiftly than that of large-sized irrigation districts in terms of the annual increasing rate (Figure 11). As a result, the IWEUC of middle self-flow irrigation districts grew at the greatest pace between 2014 and 2021 (11.94%) whereas the IWEUC of large lift irrigation districts grew at the slowest rate (4.53%). The water-saving investment in small- and medium-sized irrigation districts, for example, was higher than that in large-sized irrigation districts. For instance, in Jiangsu, the water-saving investment in small- and medium-sized irrigation districts was 201 and 184 yuan/667hm2, respectively, which was higher than that of large-sized irrigation districts (175 yuan/667hm2). Therefore, the increase of IWEUC also showed a negative correlation with the size of the irrigation district due to the greater success rate of water-saving projects in small and medium-sized irrigation districts and quicker realization of water conservation benefits.
Figure 10
Boxplot of IWEUC of different water source irrigation districts.
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Boxplot of IWEUC of different water source irrigation districts.

Figure 10
Boxplot of IWEUC of different water source irrigation districts.
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Boxplot of IWEUC of different water source irrigation districts.

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Figure 11
Annual change rate of IWEUC of different water source irrigation districts.
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Annual change rate of IWEUC of different water source irrigation districts.

Figure 11
Annual change rate of IWEUC of different water source irrigation districts.
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Annual change rate of IWEUC of different water source irrigation districts.

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Dominant influencing factors of IWEUC

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IWEUC was impacted by a number of variables, many of which were strongly tied to the environment, including soil type, engineering investment, management level, farmers' understanding of water conservation, etc. Figure 12 demonstrates the extremely significant (P < 0.01) impact of the water-saving irrigation region (X7) on IWEUC, while IWEUC was significantly impacted by precipitation (X1), actual irrigated area (X5), and water-saving irrigation engineering investment (X8) (P < 0.05). This is consistent with the conclusions of Jia et al. (2020). Other variables had a positive correlation with IWEUC, although it was not statistically significant. There was a decent correlation between the influencing elements when taking their relationship into account. For example, precipitation (X1) and evapotranspiration (X2) had a significant positive association, whereas evapotranspiration (X2) and weighting irrigation quota (X4) had a negative correlation, which could have an effect on determining the variables that influence IWEUC. As a consequence, we employed the PCA approach in this work to identify the key variables that affect IWEUC.
Figure 12
Correlation analysis between IWEUC and its influencing factors.
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Correlation analysis between IWEUC and its influencing factors.

Figure 12
Correlation analysis between IWEUC and its influencing factors.
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Correlation analysis between IWEUC and its influencing factors.

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The KMO value was over 0.5 and the significance level was less than 0.05, which suggested the acceptability of the chosen variables, according to the KMO and Bartlett's sphericity tests. In Table 3 the initial eigenvalues and variance percentage of the first two components were over 1, and the cumulative percentage reached 84.76%. With a cumulative percentage of 60.64%, the first principal component of the first two major components mostly represented the natural factors and water-saving engineering. With a cumulative percentage of 84.76%, the second principal component mainly reflected the management factors and water-saving engineering, which could essentially reflect major information of IWEUC.

Table 3

Eigenvalue and contribution rate

ComponentsInitial eigenvalue
Sum of load squares
EigenvalueVariance percentage (%)cumulative percentage (%)EigenvalueVariance percentage (%)Cumulative percentage (%)
1 5.408 60.642 60.642 5.408 60.642 60.642 
2 2.171 24.122 84.764 2.171 24.122 84.764 
3 1.110 11.334 96.098    
4 0.625 1.640 97.738    
5 0.224 1.225 98.963    
6 0.133 0.459 99.422    
7 0.027 0.355 99.777    
8 0.013 0.120 99.897    
9 0.005 0.103 100.000    
ComponentsInitial eigenvalue
Sum of load squares
EigenvalueVariance percentage (%)cumulative percentage (%)EigenvalueVariance percentage (%)Cumulative percentage (%)
1 5.408 60.642 60.642 5.408 60.642 60.642 
2 2.171 24.122 84.764 2.171 24.122 84.764 
3 1.110 11.334 96.098    
4 0.625 1.640 97.738    
5 0.224 1.225 98.963    
6 0.133 0.459 99.422    
7 0.027 0.355 99.777    
8 0.013 0.120 99.897    
9 0.005 0.103 100.000    
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The first two elements were examined in further detail in order to discover the true primary driving variables (Table 4). The load of precipitation (X1), evapotranspiration (X2), and water-saving engineering investment (X8) were prominent and made significant contributions to the first major component. Among these, the load of water-saving engineering had a significant beneficial influence on IWEUC, as shown by the fact that the load of water-saving engineering investment (X8) was the largest at 0.42, and the load of weighted irrigation quota (X4) was the least at −0.41. Departments in Jiangsu Province have increased their investments in irrigation water-saving engineering over the past several years, with the capital investment for irrigation district restoration increasing by 1.734 billion yuan compared to the previous year. The channel lining and impermeability of irrigation districts and the management level of water-saving irrigation projects have all improved thanks to uniform construction. Therefore, IWEUC has therefore steadily improved.

Table 4

Principal component loads

Influencing factorsPrincipal component
12
X1 0.377 −0.138 
X2 0.415 −0.102 
X3 −0.212 −0.410 
X4 −0.412 0.054 
X5 −0.274 0.444 
X6 −0.345 −0.344 
X7 0.289 0.497 
X8 0.421 −0.132 
X9 −0.130 0.469 
Influencing factorsPrincipal component
12
X1 0.377 −0.138 
X2 0.415 −0.102 
X3 −0.212 −0.410 
X4 −0.412 0.054 
X5 −0.274 0.444 
X6 −0.345 −0.344 
X7 0.289 0.497 
X8 0.421 −0.132 
X9 −0.130 0.469 
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In the second principal component, loads of actual irrigated area (X5), water-saving irrigation area (X7), and channel lining rate (X9) had a large positive contribution to IWEUC, which mostly indicated the state of management level and water-saving engineering. With a load of 0.497, the load of the water-saving irrigation area (X7) was the greatest among them, and the load of channel lining rate (X9) came in second with a weight of 0.469, while a load of rice planting ratio (X3) ranked the last, with a load of −0.41. Results showed that irrigation and drainage techniques, irrigation tillage, etc. had a certain effect on irrigation water consumption, which presented as the larger the water-saving irrigation area, the more uniform distribution of irrigation water (Guo et al. 2019b). The implementation of spray irrigation, micro-irrigation, and channel anti-seepage, which enhanced the channel lining rate and effectively reduced field leakage and channel leakage, were the key methods used to create the irrigation area. As a whole, upgrading water-saving irrigation construction and investment will have a positive impact on IWEUC improvement. It basically conforms to the research conclusions of Zhu et al. (2020) and Zhang et al. (2020). This paper combines single factor analysis and comprehensive factor analysis to analyze the main factors affecting the IWEUC, and gives suggestions for the improvement of the IWEUC in large, medium and small irrigation districts in Jiangsu Province. At present, there are not many relevant literatures on the influencing factors and countermeasures of the effective utilization coefficient of irrigation water in Jiangsu Province, which is a supplement to the previous results.

Economic benefit analysis of IWEUC

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To improve the IWEUC, governments at all levels have increased water-saving investment from 2014 to 2021, including continuing construction and water-saving reconstruction of large- and medium-sized irrigation districts, integrated agricultural water pricing reform, small-scale irrigation and water conservancy projects, management and protection of farmland water conservancy projects, etc. Figure 13 demonstrates that investments were rising with the exception of 2019. Small-sized irrigation districts invested the most in per acre water-saving conservation. By the end of 2021, the investment related to the improvement of the IWEUC in Jiangsu province reached 133.03 billion yuan.
Figure 13
IWEUC of different scale irrigation districts and water-saving investment in Jiangsu.
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IWEUC of different scale irrigation districts and water-saving investment in Jiangsu.

Figure 13
IWEUC of different scale irrigation districts and water-saving investment in Jiangsu.
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IWEUC of different scale irrigation districts and water-saving investment in Jiangsu.

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The percentage of investment in large-, medium-, and small-sized irrigation districts was associated with the increasing rate of IWEUC according to the prior study of influencing factors. In order to examine which size of irrigation districts were more favorable to enhancing IWEUC, we utilized the TOPSIS approach in this article to determine how to spend the investment with accuracy. Firstly, the kind of indicators was decided upon by using the rising rate of IWEUC and investment in large-, medium-, and small-sized irrigation districts as assessment indicators. The analysis revealed that the increasing rate of IWEUC was an extremely large indicator and the investment was an extremely small indicator that needed to be normalized. The results of calculating the relative proximity of each target (Table 5) revealed that the major irrigation districts had the largest relative closeness, with an S value of 0.7648, while the small irrigation districts had the lowest relative closeness, with an S value of 0.2352. Large irrigation districts were in the first place, followed by medium- and small-sized irrigation districts. Particularly, compared to medium- and small-sized irrigation districts, the economic gains for large-sized irrigation districts were the greatest given the restricted government support. The government may think about providing larger irrigation districts with greater funding in the future so that IWEUC may advance more quickly and agricultural water-saving efforts can be more effectively carried out.

Table 5

Relative closeness of the three irrigation districts

Irrigation districtsD+D−SNormalizationRank
Large-sized 0.1836 0.5961 0.7648 0.4696 1 
Medium-sized 0.2320 0.3931 0.6288 0.3861 2 
Small-sized 0.5971 0.1856 0.2352 0.1444 3 
Irrigation districtsD+D−SNormalizationRank
Large-sized 0.1836 0.5961 0.7648 0.4696 1 
Medium-sized 0.2320 0.3931 0.6288 0.3861 2 
Small-sized 0.5971 0.1856 0.2352 0.1444 3 
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Water-saving benefit analysis of IWEUC

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We examined the advantages of water conservation in Jiangsu Province during the previous 10 years based on irrigation practices and irrigation systems. Figure 14 showed that although agricultural water usage was declining, agricultural water savings were rising. The amount of water saved by agriculture as a consequence was the highest in 2017, hitting 4.6 billion m3, and it was over 13.7 billion m3 overall during the previous 10 years. The utilization of irrigation water was also declining during the same year type. Regarding the wet year, the irrigation water consumption of the irrigation district in 2020 was 24.38 billion m3, down from 0.42 billion m3 in 2016. The irrigation water consumption of the irrigation district dropped by 7% as compared to a normal median water year (2017). Due to the fact that 2019 was a particularly dry year, the irrigation water consumption of the irrigation district was 27.01 billion m3, more than that of the general dry year (2013) by 600 million m3. With the implementation of small farmland water conservancy projects, the completion of integrated agricultural water pricing reform, and efficient water-saving irrigation policies, the water-saving benefits can be realized. Meanwhile, IWEUC is being enhanced by developing a water management system, boosting the use of water-saving irrigation projects and technological measures, enhancing the management of the constructed projects, and raising the awareness of water-saving.
Figure 14
Agricultural water saving in Jiangsu Province.
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Agricultural water saving in Jiangsu Province.

Figure 14
Agricultural water saving in Jiangsu Province.
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Agricultural water saving in Jiangsu Province.

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Policy benefits encourage the improvement of IWEUC

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In 2013, Chinese central government issued ‘Assessment on Implementation of the Most Stringent Water Resources Management System’, which served as the country's first national blueprint for the goals and targets of IWEUC. The following is a concise list of the ‘Three Red Line’ goals:

(i) Establishing water resources development and utilization control red line, by 2030 the total amount of water control within 700 billion m3; (ii) Establishing water use efficiency control red line, by 2030 the water use efficiency reached or approached the world advanced level and IWEUC increased to more than 0.6.; (iii) Establishing water function area limit pollution red line, by 2030 the water quality compliance rate of water function zones increased to more than 95%.

The stepwise objectives of water resources management in 2015, 2020, and 2025 are further specified in order to meet the aforementioned red line targets. Figure 15 displayed the technical standards as well as the strategies and programs created by the governments of Jiangsu and the federal level. To create their own IWEUC policies, local governments at all levels should incorporate the criteria of the higher-level and central governments. In the last 15 years, Jiangsu government has published a number of water-saving policies, strategies, and guidelines to assist the central government's IWEUC calculation work. Farmers' awareness of water-saving has risen thanks to policy guidance, awards, subsidies, technical guidance, etc. During the 13th Five-Year Plan period, Jiangsu Province made great progress in adopting the strictest water resources management system and achieved excellent grades for five years in a row. Agriculture in Jiangsu is transitioning from a traditional paradigm to a highly effective contemporary water-saving one.
Figure 15
Important policies related to IWEUC formulated by the central government and Jiangsu government.
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Important policies related to IWEUC formulated by the central government and Jiangsu government.

Figure 15
Important policies related to IWEUC formulated by the central government and Jiangsu government.
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Important policies related to IWEUC formulated by the central government and Jiangsu government.

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Countermeasures and suggestions for increasing IWEUC

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Jiangsu Province's irrigation district construction management level accomplishments and the adoption of water-saving irrigation are reflected in the province's constantly rising IWEUC in recent years. In light of the findings of this study, the following countermeasures and recommendations for raising IWEUC are made:

  • (i)

    Increase investment in water-saving irrigation. Carry out different project inputs in large-, medium-, and small-sized irrigation districts. For example, large- and medium-sized irrigation districts increase investment in water-saving renovation projects, and small-sized irrigation districts increase investment in small-sized irrigation and water conservancy. IWEUC will continuously increase annually as the project's quality is enhanced, which will assist Jiangsu economically and by conserving water.

  • (ii)

    Strengthen the construction of water-saving projects. Choose the best irrigation and water conservation technology for the local conditions, and progressively implement digital agricultural irrigation information to improve IWEUC. For large- and medium-sized irrigation districts, we should deploy automatic water measurement facilities and soil moisture monitoring facilities to improve the irrigation water measurement system. New efficient water-saving initiatives should be used in small-sized irrigation districts. By updating outdated water conveyance pipelines such as earth canals and stone canals, and adopting advanced low-pressure pipe irrigation to increase channel lining rate and reduce leakage loss, IWEUC will be improved gradually.

  • (iii)

    Improve irrigation district management. Establish the management system of ‘Irrigation district + water users association + specialized service organization’ and form the operational mechanism of ‘policy guidance + socialized service support + autonomous management’. At the same time, we should deepen the implementation of integrated agricultural water pricing reform to improve the construction of project management and the managers' professional level. What is more, the government should continue to promote the management of farmers' water associations and encourage farmers to participate in management to raise users' awareness of water-saving. Above all, it will have a positive impact on IWEUC.

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The irrigation water effective utilization coefficient is an essential indicator of agricultural water use efficiency. Clarifying the inter-annual variation of IWEUC in Jiangsu, thoroughly examining its key influencing variables, and investigating its economic and water-saving advantages will aid the government in enhancing irrigation water efficiency, investigating the potential for agricultural water-saving, and developing workable regional plans. By reviewing the IWEUC in recent years in Jiangsu, we can draw the following conclusions:

  • (i)

    As a developed province, Jiangsu has a utilization rate of irrigation water, and IWEUC increased annually, with a rate of 8.64%. In 2015, the Jiangsu Provincial Department of Water Resources promulgated the ‘Notice on strengthening the construction of metering facilities for rural water conservancy projects’ and it placed a focus on metering facility management and construction enhancement beginning in 2016. That resulted in a higher increase rate in the preliminary planning period than that in the mid-term and post-consolidation period., With the completion of integrated agricultural water pricing reform in the post-consolidation period, the level of agricultural irrigation water metering facilities increased with steady growth.

  • (ii)

    IWEUC of different sizes and types in Jiangsu Province showed a consistent development pattern from 2014 to 2021. IWEUC and its increasing rate was found to be negatively correlated with the size of irrigation districts, which were classified as ⁠. IWEUC of lift irrigation districts was higher than that of self-flow irrigation districts when comparing the various types of water sources. Due to the smaller area and management challenges, the IWEUC of small- and medium-sized irrigation districts increased more quickly than that of large-sized irrigation districts. The IWEUC of middle self-flow irrigation districts had the fastest growth rate of 11.94%, while that of large lift irrigation districts showed the slowest rate of 4.53%.

  • (iii)

    IWEUC was affected by various factors, results showed that the water-saving irrigation areas had a very significant impact on IWEUC (P < 0.01), while precipitation, actual irrigated area, and water-saving irrigation engineering investment had a significant effect on IWEUC (P < 0.05). Other factors were positively correlated with IWEUC, but were not significant. Strengthening the construction of water-saving engineering and optimizing management level had a high positive impact on IWEUC, according to the PCA method, which showed that the load of water-saving engineering investment was the largest, with a load of 0.42 and in the second principal component, the load of water-saving irrigation area was the largest, with a load of 0.497.

  • (iv)

    The economic gains for large irrigation districts were superior to those for small irrigation districts, even with the restricted government assistance. The government may think about providing larger irrigation districts with greater funding in the future so that IWEUC may advance more quickly and agricultural water-saving efforts can be more effectively carried out. In the past decade, agricultural water use declined while agricultural water conservation rose. The amount of agricultural water-saving was the largest in 2017, reaching 4.6 billion m3, and the cumulative water-saving quantity was over 13.7 billion m3. Under the same year type, the irrigation water use was decreasing as well.

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This study is supported by the Water Resources Science and Technology Project of Jiangsu Province (Grant No. 2019043).

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All relevant data are included in the paper or its Supplementary Information.

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The authors declare there is no conflict.

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.
Journal of Physics Conference Series
1622
,
012087
.
https://doi.org/10.1088/1742-6596/1622/1/012087.
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