The Evaluation of Groundwater Resources Value of Beijing Based on Emergy Theory

Accurate yet valid evaluation of values of groundwater resources is difficult.However, it is of an urgent need. Based onwater resource system, the emergy synthesis of the ecological economics was used to make a systematic study on the assessment of the quantity of groundwater resources. Taking Beijing in 2012 as an example, the values of groundwater for residents life subsystem, the industrial subsystem, and the agricultural subsystem are 7.64, 6.00, and 3.25 billion Yuan, accounting for 45.24, 35.5, and 19.24% of the total value, respectively. The total value of the underground water accounts for 1.51% of the GDP in Beijing for that year. Meanwhile, Contribution Rate of Groundwater Resources (GWCR) in Beijing decreased in the following order: groundwater contribution rate for industry (GWCRI 4.52%), groundwater contribution rate for agriculture (GWCRA 3.24%), and groundwater contribution rate for residential life (GWCRL 0.71%).The conclusions will provide important basis for the government’s scientific decision to improve the level of comprehensive management of water resource.


Introduction
As a part of the natural resources, the groundwater provides valuable water for most people to support agricultural and industrial production activities.About two-thirds of people in China use groundwater as their drinking water, and about two-thirds of cities and farmlands take groundwater as their main water supply, especially in Northern China, where the development is heavily dependent on the exploitation of groundwater [1].The evaluation of groundwater resources is a practical problem to be solved in social development.It is important to use the groundwater reasonably and to realize the coordinated development between economic society and environment.
The above-mentioned methods all attempt to monetize water resources and human economy activities, to use the currency as the only way to measure wealthy, but currency cannot measure everything, particularly the essence of nature and laws.Water (groundwater) is a kind of natural resource and its value cannot be measured by money totally because the currency in circulation does not pass through natural world.Currency is only a tool to measure human's role and contribution in economic activities, not the role and contribution of economy and nature.Groundwater provides the vast majority of people with valuable water resource and sustains agriculture and industry.At the same time, the pollution of water mainly arises from human's activities [19].Therefore, research on groundwater resource value can be made from its contribution to industrial production, agricultural production, and residential life.
The new method of groundwater evaluation is the emergy theory of ecological economics.Emergy theory is reviewed as the value theory of environment and natural resources.

Waste water
The water ecological economic system of Beijing $ Figure 1: Diagram of eco-economic inputs and outputs within and outside the RWEES (regional water ecological-economic system).
The essence of the emergy theory is translating different forms of energy and materials into solar energy.In 2000, the emergy theory was applied to the field of water resources by Buenfil for the first time.Buenfil simulated and optimized the allocation of water in city, agriculture, and environment of Florida, America.In 2001, Buenfil calculated the emergy transform rates of the main rivers, aquifers, and eight water plants in Florida.Xie [20] analyzed the water environment value of Tumen River Basin using the emergy theory.Chen [21] applied the emergy method to the evaluation of natural water resources and regarded coastal county in southern China as an example for practical application.Lv [22] conducted a systematic study of emergy evaluation of ecological economic value of water resources.
Based on the energy recycling and transformation in water eco-economic system and the construction principles of energy and emergy network, the energy and emergy network of water eco-economic system and its subsystems are constructed in this paper, including industrial subsystem, agricultural subsystem, and residential subsystem.In the light of the current situation of economy development and water exploitation in Beijing, the groundwater resource value was checked from 2008 to 2012, which will provide theoretical basis and techniques for the proper decision and evaluation of water exploitation.

Theory and Method
Emergy, specifically solar emergy, is the available solar energy used up directly and indirectly to make a service of product [23].Therefore we can measure the emergy of all kinds of energy based upon the solar energy.The solar emergy owned by any sources, products, or services is the amount of solar energy they used directly or indirectly for their formation, and its unit is solar emjoules (sej).

The Energy Network of Water Resource System and
Its Subsystem (1) The Energy and Emergy Network of Water Eco-Economic System.According to the basic structure of water resources eco-economic system and the main condition of ecologicaleconomic flow including energy sources, material, and information, the energy network of water resources ecologicaleconomic system is constructed (Figure 1).The basic structure of regional water ecological-economic system, the relationship of ecological and economic flow and its main direction, water circulation flow path, and the relationship between economic-social production and ecological environment will be clear.And then emergy/dollar ratio (EDR) is calculated as follows: GWCR  = Emergy of Groundwater within Agriculture All Emergy Input within Agriculture , GWCR  = Emergy of Groundwater within Residents life All Emergy Input within Residents life . (4)

Transformity of Different Water Bodies with the Method of Emergy Calculation.
The biggest challenge of the emergy analysis is the calculation of transformity (Tr) of all sorts of energy, material, information, and service.So far, lots of significant achievements of the international emergy research have been accomplished.Odum and other researchers over the world (such as Brown et al. [24]) calculated the transformity of the emergy of the main energies and substances.With this transformity of the emergy we can do some generic systematic emergy analysis that could be conducted.It is necessary to calculate more detailed transformity of the emergy between resources and substances according to professional systems.For example, for the ecologically economical systems of the water resources, just the rainwater emergy transformity is not enough; calculating more detailed classifications of the water solar emergy transformity is required.
The UEV (unit of emergy value) of a system can be considered as an efficiency indicator.For example, Brown et al. [24] stated that "UEVs are inversely related to the system efficiency on the scale of the biosphere." In other terms, a more efficient overall use of resources by the coupled humannatural system has a lower UEV.The UEVs of the natural water, the engineering water, and the recycled water were calculated, respectively, as follows: UEV (7) And per-capita water supply is 173 m 3 , which is lower than the world average (Figure 2).Groundwater resource is not only a basic resource for the development of Beijing, but also strategic resources and the important guarantee for Beijing's development.With groundwater accounting for 1/2 of the city's water supply, Beijing is one of the few big cities that regard groundwater as the main source of water supply.

Case Study
With the rapid development of the urban construction and the process of rural urbanization, an increase of the urban population, the conflict between supply and demand of water in the city is more serious.The excessive exploitation of groundwater has caused a series of environmental problems, such as land subsidence and ground fissure, and shortage of groundwater has become a bottleneck of the economic and sustainable development of Beijing.

Results and Discussion
(1) Calculation of EDR in Beijing Based on the Regional System Emergy Analysis.According to a comprehensive analysis of the main energy flow, material flow, and monetary flow inside and outside of Beijing water resources ecological-economic system, the emergy index datum, including renewable resources emergy (EM  ), nonrenewable resources emergy (EM  ), feedback input emergy (EM  ), and the system emergy export (EM EX ), the total emergy used (EM  ) of the system emergy yield (EM  ), and annual water emergy (EM  ), was calculated.The complex emergy network chart of the regional water ecological-economic system (RWEES) in Beijing was constructed (Figure 3).After arranging the raw data, analysis of energy, material, and monetary flows in Beijing, the emergy flow of all kinds of resources, material, and monetary in the system was classified and established.EDR (emergy/RMB) was calculated (Table 1).
(2) Calculation of Transformity of Different Water Bodies in Beijing.The natural water in Beijing can be generally divided into two kinds: surface water and groundwater.Based on the method of the calculation of transformity of different water bodies, transformity of surface water, groundwater, and engineering water from 2008 to 2012 in Beijing was counted (Table 2).
In accordance with the scale of the water supply of the 9th Water Plant which takes the surface water as source water and the 8th Water Plant which takes groundwater as the source water in Beijing, based on the Standards of Urban Water Supply Construction Project, the input and output amounts of emergy of the water plant were reckoned.The emergy transformity of different water bodies in Beijing was calculated as shown in Table 3 with formulas (5), (6), and (7) above and the original data reference from the following references: [30][31][32][33][34][35].
(3) Emergy Analysis of Groundwater Resources Value regarding the Industrial Subsystem as an Example.According to the main directions of energy flow, material flows in the industrial subsystem, and the relations of production in the system in Beijing, the industrial subsystem emergy network was established (Figure 4).Through the collection, classification, and collation of the original data of energy, material, and money flows of Beijing industrial subsystem, the emergy flow of the industrial subsystem from 2008 to 2012 was obtained.Taking 2012 as an example, the calculation result was shown in Table 4.
Among them, the solar energy and the wind energy are obtained from all the Beijing area.Nonrenewable resources are calculated on the basis of the data of standard coal given in the Beijing Statistical Yearbook.The raw materials, labor, operation expenses, and fixed assets are expressed in currencies.
With formula (2) and summarizing the data in Table 4 (the data of 2008-2011 can't be shown in this paper, for the limited space), the emergy of groundwater for industry and GWCR  of Beijing from 2008 to 2012 was shown in Table 5.For the better comparison of different years, the amount of money involved in the process of calculation is based on the comparable prices calculated of 2008.Transformity of Table 4 marked with " * " sited from Lv [22] and Odum [23].Other Tr without " * " are calculated with the original data.
Similarly, the emergy value of the groundwater for agricultural and living subsystems can be obtained.The summary of groundwater resources value in Beijing was shown in Table 6.
According to the results, the groundwater emergy value and monetary value of the industrial subsystem both show a steady trend from 2008 to 2012.Monetary value per volume of groundwater for industry was slightly decreased in the later 2 years because of the promotion of water-saving awareness and the implementation water saving action.
The groundwater emergy value and monetary value of the agricultural subsystem in Beijing kept a stationary fluctuation trend.Compared to a year earlier, the emergy value of the agricultural subsystem in the last three years rose slightly.This is due to the effect of agricultural irrigation and water saving policies; in addition, an increase in efficiency of farming is another reason.
In addition, a rising trend in these years of groundwater resources value can be seen in general, although there were slight fluctuations in the middle years.For example, monetary  (4) The Summary of GWCR in Beijing.Comparing GWCR  and GWCR  in Beijing, for 5 years the average GWCR I was 0.944% and the average GWCR  was 4.38% (Table 7).This is because agricultural production is generally dependent on the supply of water, but the degree of industrial production relying on water is low.In addition, urban water supply is mostly from reservoir water but rural wells water supply is mostly from groundwater in Beijing.GWCR  in Beijing showed a downward trend (Figure 5), falling from 4.42% in 2008 to 3.24% in 2012.On the one hand, the residents' awareness of water saving is strengthened, and the South to North Water Diversion Project is gradually put into use.

Conclusions
Based on the principle of water cycle and the emergy theory of ecological economy, the frame of emergy evaluation of groundwater resources is constructed.
(1) The Evaluation of the Importance of Groundwater as a Basic Elements Involved in Each Subsystem.As a basic element for the residents' life, groundwater also supports the industry's production activities.Taking Beijing in 2012 as an example, in terms of monetary value of groundwater from big to small sorting, followed by groundwater for residents, for industrial, and for agricultural, its monetary value was 7.64, 6.00, and 3.25 billion yuan, accounting for 45.24%, 35.52%, and 19.24% of the total value, respectively.The total monetary value of the groundwater (16.89 billion yuan) accounts for 1.51% of the GDP (1118.059 billion yuan based on the comparable price of 2008) in Beijing.
(2) Predicting the GWCR of Each Subsystem.In 2012, the GWCR of each subsystem including GWCR  , GWCR  , and GWCR  are 4.52%, 3.24%, and 0.71%, respectively.By further understanding the true value of groundwater and strengthening integrated management to water resources, the of Natural water = Total Emergy of the watershed rainfall (sej/a) Mass of The catchment water capacity per year (m 3 /a) = (Rainfall per year × Gibbs energy of rain × Tr of the Rain) × (Mass of Total water per year ÷ Refresh Cycle Time) Emergy of Engineering water Input per year (sej/a)) × (Mass of Total water per year (m 3 /a)) Emergy input within Waste water treatment per year (sej/a)) × (Mass of Total Recycled water per year (m 3 /a)) −1 .

Figure 4 :
Figure 4: Figure of energy flows for Beijing industrial subsystem network.

Figure 5 :
Figure5: The summary table of contribution rate of water resources.

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Table 1 :
The Summary of the main emergy indexes about the water system of Beijing (unit: 10 20 sej).The data of Table1have been summarized.The regional data reference is from the following books: [25, 26].
Year Data Figure 2: The population of permanent residents, water supply, and gross domestic product (GDP) of Beijing.Source: [25].

Table 3 :
Engineering water, tap water, and recycled water emergy per volume.

Table 4 :
Emergy inputs and outputs within and outside BIS (Beijing industrial system), 2012.
3, which is as much as 14.99 ¥/m 3 in 2012 which is much lower than the average price of residents water (5 ¥/m 3 ) in Beijing.

Table 6 :
The summary table of Beijing groundwater value.

Table 7 :
The Summary table of contribution rate of water resources (unit: %).