Comprehensive evaluation of the effect of regional groundwater overexploitation restoration

Groundwater is an important part of water resources, with important resource functions and ecological environment functions (Chen et al. 2020). The sustainable development of groundwater is of great significance for supporting economic and social development and maintaining ecological environment stability. With the increase in population and the continuous development of the economy and society, groundwater has been widely developed and utilized. At present, the global groundwater exploitation has exceeded 1,000 billion m³/a (Dillon et al. 2019). Global groundwater exploitation accounts for 33% of total water withdrawals and more than two billion people depend on groundwater, resulting in excessive groundwater consumption in many regions of the world (Sun et al. 2021).

In China, due to long-term overexploitation, groundwater in some areas has been seriously overdrawn, forming a large-scale regional landing funnel and causing environmental and geological problems such as ground subsidence and ecological degradation (Guo et al. 2021; Yu et al. 2021) while leading to aggravated groundwater pollution. Most of groundwater overexploitation areas are distributed in northern China, and the overexploitation area in the plain is nearly 300,000 km² (Yu et al. 2018). The area of groundwater overexploitation in Hebei Province is approximately 69,700 km², accounting for 90% of the plain land area of Hebei Province and approximately 23% of China's groundwater overexploitation area (Yu et al. 2020). The North China Plain, where Hebei Province is located, is the world's largest groundwater funnel area (Qin et al. 2020).

In 2014, to control the increasingly serious problem of groundwater overexploitation in Hebei Province, the Chinese government launched a pilot project to explore groundwater overexploitation restoration measures and summarized the experience in order to provide support for other parts of China with similar groundwater challenges. In 2017, the scope of groundwater overexploitation restoration was extended to Shandong Province, Shanxi Province, and Henan Province. In 2019, China further intensified groundwater overexploitation restoration measures in the Beijing–Tianjin–Hebei region. The main measures were to use rivers and lakes to recharge groundwater under the premise of ensuring normal water use for urban and rural life and for production purposes in areas with serious groundwater overexploitation and better water resource conditions (Chen et al. 2021). With the increasing groundwater overexploitation restoration measures in Hebei Province, it is urgent to scientifically evaluate the effect of groundwater overexploitation restoration, so as to provide a decision-making basis for further formulating groundwater overexploitation restoration measures.

The evaluation indicator system is the basis for evaluating the effect of groundwater overexploitation restoration. Selim et al. (2014) evaluated the effect of groundwater overexploitation restoration on the environment in Aswan, Egypt, using groundwater level as an evaluation indicator; Chatterjee et al. (2018) used groundwater level as an assessment indicator to analyze the impact of four groundwater management measures, viz., regulation of groundwater extraction, artificial recharge to groundwater, on-farm irrigation management practices and water conservation practices such as recycle and reuse of water; Yang (2020) selected five indicators, including river surface, groundwater infiltration, groundwater level, river water quality, and public happiness, to evaluate the effect of river and lake recharge to groundwater in North China; Lei et al. (2021) analyzed the restoration effect of groundwater overexploitation zones in Korla City by selecting indicators related to the implementation status of engineering measures and the status of groundwater level and quantity.

Most previous studies have used groundwater level variation and the completion of restoration measures as evaluation indicators for the effect of groundwater overexploitation restoration, without considering the impacts of the restoration measures on the economic society and ecological environment. Groundwater overexploitation restoration not only affects the groundwater system, but also significantly affects the economic society system and the ecological environment system. During the implementation of groundwater overexploitation restoration measures, the rate of groundwater level decline has decreased, the balance of groundwater system exploitation and replenishment has gradually recovered, the area of groundwater landing funnel has decreased, the original method of groundwater development and utilization by the economic society has changed, the urban living and industrial and agricultural groundwater consumption has been reduced, the water quality of rivers has improved, the ecological water quantity and water surface area of rivers have increased, and the ecological environment has been improved. Therefore, the establishment of an evaluation indicator system for groundwater overexploitation restoration that covers the groundwater–economic society–ecological environment (GESEE) system helps to scientifically evaluate the effect of groundwater overexploitation restoration.

The objectives of this paper are to analyze the effect of groundwater overexploitation restoration on the GESEE system; to construct an evaluation indicator system for the effect of groundwater overexploitation restoration covering the GESEE system; to establish an evaluation method for groundwater overexploitation restoration; and to quantitatively evaluate the effect of groundwater overexploitation restoration in Hebei Province and cities from 2014 to 2019 to provide a reference for formulating restoration measures of groundwater overexploitation.

Hebei Province is in the North China Plain, with an average annual precipitation of 531.7 mm. The spatial and temporal distribution of precipitation in Hebei Province is uneven, with a large annual variation; 70–80% of the annual precipitation is concentrated from June to September. Spatial distribution of precipitation shows decreases from the northwest to southeast. Hebei Province, with a total area of 188,000 km², consists of 11 cities. In 2019, the total population of Hebei Province was approximately 75.92 million, of which the urban population was 43.74 million, the annual regional GDP was 3,510.5 billion yuan, and the crop's planting area was approximately 80,560 km².

The average annual overexploitation of groundwater in Hebei Province is 3.801 billion m³, including 1.578 billion m³ of shallow groundwater and 2.224 billion m³ of deep confined water. In 2014, the Chinese government launched a groundwater overexploitation restoration pilot project in Hebei province. The pilot project took 49 counties in four cities of Hengshui, Cangzhou, Xingtai, and Handan, where deep groundwater overexploitation was the most serious, as the pilot areas. In 2019, the groundwater overexploitation restoration in Hebei Province covered all 11 cities in the province, including 128 counties where overexploitation areas existed. Since the groundwater overexploitation restoration pilot project in 2014, the amount of groundwater exploitation in Hebei Province decreased from 14,207 million m³ in 2014 to 9,644 million m³ in 2019.

The basic data for the evaluation of the effect of groundwater overexploitation restoration are mainly derived from the ‘Hebei Provincial Water Resources Bulletin’, ‘Hebei Provincial National Economic and Social Development Statistical Bulletin’, ‘Hebei Provincial Economic Yearbook’, and ‘Hebei Provincial Geological Environment Status Bulletin’, as well as groundwater monitoring, groundwater overexploitation area evaluation, water resources surveys and evaluation, groundwater overexploitation planning and other achievements.

Through groundwater overexploitation control measures, we can effectively reduce the amount of groundwater extraction, suppress the amount of groundwater overexploitation, and either decrease the rate of groundwater level decline or slowly raise the groundwater level. The rise in groundwater levels increases the natural discharge capacity of the groundwater system to surface water bodies and consequently to river baseflow. The reduced thickness of the unsaturated zone results in an increased ability for precipitation or lake infiltration to recharge groundwater.

Adjusting planting structures may result in reduced food production and affect farmers' income. The development of agricultural water-saving irrigation can increase the area of water-saving irrigation and reduce the amount of groundwater use in agriculture. The implementation of industrial water conservation and emissions reduction can reduce industrial groundwater use. Promoting water resources tax reform, which levies for groundwater higher than surface water for similar uses, can guide users to reduce extraction on their own initiative.

The groundwater level rises, reducing the depth of water in the center of the groundwater landing funnel, thereby slowing down the rate of ground settlement so that ground cracks no longer lengthen or increase in number. The development of non-agricultural crops to replace agricultural crops, the implementation of returning farmland to forests and the creation of large-scale continuous forests can increase forest cover. Through the implementation of river and lake recharge to groundwater, the ecological water quantity and surface area of rivers increases, and the groundwater level around rivers raises.

Based on scientificity, feasibility, regionality, comprehensiveness and representativeness and in full consideration of the situation of groundwater overexploitation and its restoration measures implementation in Hebei Province and various cities, 16 evaluation indicators covering the GESEE system are constructed. The evaluation indicator system of the groundwater overexploitation restoration effect in Hebei Province is shown in Table 1.

Evaluation indicators are divided into two categories: positive and negative. The positive indicator refers to an increase in the index of groundwater overexploitation restoration effect, where the larger the value indicates a better effect; the negative indicator refers to a decrease in the index of groundwater overexploitation restoration effect, where a larger value indicates a worse effect.

The comprehensive evaluation method of ‘single indicator quantification–multi-indicator synthesis–multi-criterion integration’ in the harmonious quantitative evaluation method is adopted (Zuo & Mao 2012), which has been widely used in water resources analysis and evaluation. The method consists of three steps: single indicator quantification, multi-indicator synthesis, and multi-criteria integration.

Since the dimensions of the evaluation indicators are not identical, to facilitate calculation and comparative analysis, the indicators of different dimensions are mapped to the [0,1] interval in order to calculate the groundwater overexploitation restoration effect index of each indicator. Each evaluation indicator has five characteristic node values, including the worst value (a), poor value (b), passing value (c), better value (d), and optimal value (e). The characteristic node values methodically determined by the relevant research results, the relevant norms or standards issued by the state or locality, and the relevant groundwater overexploitation area planning by the industry are shown in Table 2 (Yang et al. 2012; Wang & Yang 2013).

Based on the calculation of the groundwater overexploitation restoration effect index for a single indicator, the groundwater overexploitation restoration effect index of each criterion layer and the target layer is calculated according to the weighted summation method. The indicator weight is determined comprehensively by using the analytic hierarchy process and the entropy weight method (Li et al. 2018; Liu et al. 2019).

The groundwater overexploitation restoration effect index reflects the regional groundwater overexploitation restoration effect, and the larger the groundwater overexploitation restoration effect index is, the better the groundwater overexploitation restoration effect. Referring to and drawing on relevant research results (Yang et al. 2012), combined with the actual situation in Hebei Province, the groundwater overexploitation restoration effect is divided into five grades according to the effect index: Excellent [1,0.8), Good [0.8,0.6), Medium [0.6,0.4), Fair [0.4,0.2), Poor [0.2,0), and expressed by E, G, M, F, P, respectively.

Groundwater overexploitation engineering restoration measures need a certain period to fully have an effect. For example, groundwater water replacement for agriculture and industry can only be implemented after the completion of water diversion projects and water transmission network pipeline projects, which require a certain period for construction and a certain amount of time for the projects to fully reach their design capacity after completion and operation. The effect of groundwater overexploitation restoration has a lag, such as the groundwater landing funnel area, even if the groundwater exploitation reduction task is completed, the groundwater landing funnel area may still increase. Therefore, the index of groundwater overexploitation restoration effect in Hebei Province from 2014 to 2015 is low.

After Hebei Province strengthened the management of groundwater abstraction permits, the negative indicator groundwater exploitation coefficient (C₁) continued to decrease. The implement of ecological water recharge to rivers and lakes led the positive indicator change rate of river base flow (C₅) to generally show an increasing trend. Through industrial, agricultural and domestic water conservation, adjusting the structure of planting and industry, and promoting water resource tax reform led to a continuous decline in the negative indicators of proportion of groundwater supply (C₆), proportion of agricultural groundwater (C₇), proportion of industrial groundwater (C₈), average irrigation water per mu (C₉) and water consumption per 10,000 yuan industrial added value (C₁₀). The negative indicator groundwater overexploitation ratio (C₁₃) continued to decrease. Through the return of farmland to forest, the positive indicators of vegetation coverage (C₁₅) and no increase in ground fissures in N years (C₁₆) gradually became larger. Hence, the groundwater overexploitation restoration effect grade demonstrated an improving trend.

According to the above results, ‘Reducing exploitation’ contributes more to the effect of groundwater overexploitation restoration than ‘Increasing water sources’. Li et al. (2021) also studied the effect of different measures on the groundwater overexploitation restoration efficiency and came to a similar conclusion that ‘Reducing exploitation’ such as adjusting planting structures and water-saving irrigation is more efficient than ‘Increasing water sources’ such as farmland water conservancy projects. Moreover, ‘Increasing water sources’ measures such as the replacement of water sources needs to build pipelines and other projects, and the implement of ecological water recharge to rivers and lakes requires rivers and lakes to complete the cleaning task. These measures require significant investment and will take some time to begin to work. In addition, the external transfer of water is unstable, with a certain degree of uncertainty and the same dryness and abundance. Although ‘Increasing water sources’ measures are more involved and have a relatively low restoration effect, they are still indispensable in order to meet water demand. Measures such as the replacement of water sources can be used to coordinate water consumption while suppression of groundwater exploitation is taking place.

In summary, strict control of exploitation and fundamental reduction of consumption is the key to controlling the problem of groundwater overexploitation, and increasing water sources is an indispensable way. There is a need to consider the priority of groundwater overexploitation restoration measures, to appropriately increase the scale of investment in high-efficiency measures, to optimize the scale of other measures, and to consider the sustainability of restoration as well as the synergies between long-term and short-term restoration. Therefore, in the process of groundwater overexploitation restoration, reasonable tasks and targets should be set for suppressing groundwater exploitation, and the replacement of water sources and the implement of ecological water recharge to rivers and lakes should be used as supplementary means.

The measures that have a greater impact on each city in Hebei Province can be analyzed from the changes in the groundwater overexploitation restoration effect index of various indicators in various cities. For the seven cities of Baoding, Cangzhou, Handan, Langfang, Qinhuangdao, Shijiazhuang, and Zhangjiakou, both ‘Reducing exploitation’ and ‘Increasing water sources’ measures have a large effect. In particular, the implement of ecological water recharge to rivers and lakes in Baoding causes significant changes in river baseflow and plays an important role in the management of groundwater overexploitation. For Hengshui city, the measures of controlling groundwater use in ‘Reducing exploitation’ and measures to replace groundwater sources with additional water sources in ‘Increasing water sources’ contribute significantly. For Tangshan and Xingtai cities, the measures of reducing groundwater overexploitation in ‘Reducing exploitation’ are more significant. In the future process of groundwater overexploitation restoration, each city should strengthen the measures that have a greater impact on the effect of groundwater overexploitation restoration in that city, so that they can be as effective as possible, while supplementing the measures that are insufficient.

This paper analyzed the effect of groundwater overexploitation restoration on the GESEE system, constructed an indicator system for evaluating the effect of groundwater overexploitation restoration, and evaluated the effect of groundwater overexploitation restoration in Hebei Province and various cities. This research is of great significance for promoting the process of groundwater overexploitation restoration and realizing the sustainable use of groundwater resources. The main conclusions are as follows.

• (1)

  During 2014–2019, the effect of groundwater overexploitation restoration in Hebei Province was remarkable, and the effect grade was improved from fair to good. The effect grade of different subsystems was upgraded from poor, fair, or medium to medium or good. All cities achieved results in groundwater overexploitation restoration. By 2019, all cities in Hebei Province had achieved a medium or higher groundwater overexploitation restoration effect grade, and there was one city with a groundwater overexploitation restoration effect grade of excellent.

• (2)

  Strict control of exploitation and reduction of consumption is the key to solving the problem of groundwater overexploitation, and ‘Increasing water sources’ measures such as the replacement of water sources and the implementation of ecological water recharge to rivers and lakes are indispensable and important means. The measures that have a greater impact on the effect of groundwater overexploitation restoration are different for various cities. Each city should strengthen the measures that have a greater impact on the effect of groundwater overexploitation restoration in that city while supplementing the measures that are insufficient.

Although this paper comprehensively considered the impact of groundwater overexploitation restoration on the GESEE system, many factors influence the effect of groundwater overexploitation restoration. Some indicators, such as the better groundwater quality rate and the ground subsidence decline rate, are not included in the indicator system in Hebei Province due to the difficulty of collecting relevant data, which has a certain influence on the results. In future studies, these data need to be collected in a targeted manner to further consolidate the basic information.

This work was supported by the National Natural Science Foundation of China (No. 52079125).

Data cannot be made publicly available; readers should contact the corresponding author for details.

The authors declare there is no conflict.