**2. Study Area and Division of Integrated Zones**

Dalian covers 43,014 km2, of which 13,739 km2 is land. The city's multi-year average total water resources are 3.14 × 109 m3, of which surface water resources are 3.05 × 109 m3, and the regional distribution, as well as inter- and intra-annual changes in the runoff in each basin, are extremely uneven, making it a water-poor area [19]. There are more than 300 rivers in the urban area, which are divided into the river systems along the Yellow Sea in eastern Liaodong and the river systems along the Bohai Sea in the eastern Liaodong Bay. There are 57 rivers that flow into the sea, along with a catchment area of more than 2.00 × <sup>10</sup><sup>7</sup> <sup>m</sup><sup>2</sup> [20]. There are 69 reservoirs of various types, with a total annual storage capacity of 1.32 × 109 <sup>m</sup>3, of which 22 are the main drinking water sources. Dalian is rich in wetland resources, with a total area of about 3.58 × <sup>10</sup><sup>9</sup> <sup>m</sup>2, including 2.42 × 109 <sup>m</sup><sup>2</sup> of offshore and coastal wetlands, 1.04 × <sup>10</sup><sup>9</sup> <sup>m</sup><sup>2</sup> of artificial (coastal) wetlands, 1.15 × 108 <sup>m</sup><sup>2</sup> of river wetlands, and 3.00 × 108 <sup>m</sup><sup>2</sup> of marsh wetlands.

Figure 2 shows the geographical position and study regions of Dalian. To reflect different water environmental functions and water resource utilization in terms of time and space, the study area was divided into 37 integrated zones (i = 1–37 represent I, II, III, IV, V, VI, VII, VIII, IX, X, XI, XII, XIII, XIV, XV, XVI, XVII, XVIII, XIX, XX, XXI, XXII, XXIII, XXIV, XXV, XXVI, XXVII, XXVIII, XXIX, XXX, XXXI, XXXII, XXXIII, XXXIV, XXXV, XXXVI, and XXXVII) and six administrative regions (i = 1–6 represent four districts (Xigang, Shahekou, Ganjingzi, and Zhongshan), as well as Lvshunkou, Jinpu, Wafangdian, Pulandian, and Zhuanghe). Figure 3 shows the relationship between regional pollutant emissions and water distribution, including pollutant emission directions and proportions. The values show the proportion of pollutant emissions generated from region j and discharged into the water environment zone i.

**Figure 2.** Geographical position and study regions of Dalian.

**Figure 3.** Relationship between regional pollutant emissions and water distribution.

#### **3. Model Formulation**

*3.1. Model Development*

It is often necessary to combine two-stage stochastic programming (TSP) [21] with Interval Linear Programming (ILP) to deal with uncertain factors in practical problems. Using the maximization problem as an example, the ILP is combined with the TSP to obtain the interval two-stage stochastic optimization model (ITSP), which can be expressed as:

$$\text{maxf}^{\pm} = \mathbf{c}^{\pm} \mathbf{x}^{\pm} - \sum\_{\mathbf{s}=1}^{N} \mathbf{p}\_{\mathbf{s}} \mathbf{q}(\mathbf{y}^{\pm}, \omega\_{\mathbf{s}}^{\pm}) \tag{1a}$$

and

$$\mathbf{A}^{\pm}\mathbf{x}^{\pm} \le \mathbf{b}^{\pm} \tag{1b}$$

$$\mathbf{T(w\_s^{\pm})} \mathbf{x^{\pm}} + \mathcal{W}(\omega\_s^{\pm}) \mathbf{y^{\pm}} = \mathbf{h(w\_s^{\pm})} \tag{1c}$$

$$\mathbf{x}^{\pm} \ge \mathbf{0}, \ \mathbf{y}(\omega\_{\mathbf{s}}^{\pm}) \ge \mathbf{0} \tag{1d}$$

Model 1 can be solved by transforming into sub-models of upper bound and lower bound objective functions through an interactive algorithm [14]. Then, the optimal solutions for Model 3 can be obtained as f ± jopt = f − jopt, f<sup>+</sup> jopt , x± jopt = x− jopt, x<sup>+</sup> jopt and y± lsopt = y− lsopt, y<sup>+</sup> lsopt . For more details, refer to [14,22].

The research planning period will last until 2035 and will be divided into three phases: 2021–2025 (phase I), 2026–2030 (phase II), and 2031–2035 (phase III). Three flow scenarios are designed as low, medium, and high, reflecting different probabilities of water resource availability and environmental carrying capacity with different flow scenarios. The ecosystem is a prerequisite for economic and social development, and the ecological value needs to be taken into account while optimizing the allocation of water resources to achieve synergy between ecological and water use benefits. Model ecological benefits primarily include the value of ecosystem-regulating services, which can be defined as the sum of the value of ecosystems for sustainable economic and social development and human well-being [23]. This study considers four main values of water ecosystem regulation services: water purification value, hydrological regulation value, water conservation value, and research and cultural value. In the model, the difficulty of clarifying parameters, such as the number of surface water resources and water consumption quota in Dalian, can be expressed in discrete intervals based on their maximum and minimum values. The ITSP model of Dalian coupled with ecological value factors can be formulated as follows:

$$\max \mathbf{f}^{\pm} = \mathbf{f}\_1^{\pm} + \mathbf{f}\_2^{\pm} - \mathbf{f}\_3^{\pm} - \mathbf{f}t\_3^{\pm} - \mathbf{f}\_4^{\pm} - \mathbf{f}t\_4^{\pm} - \mathbf{f}\_5^{\pm} \tag{2a}$$

where f<sup>±</sup> is the total expected system benefit (104 CNY) over the planning periods.

(1) Sectors of water utilization benefits:

$$\mathbf{f}\_{1}^{\pm} = \sum\_{\mathbf{j}=1}^{6} \sum\_{\mathbf{k}=1}^{3} \sum\_{\mathbf{t}=1}^{3} \mathbf{L}\_{\mathbf{t}} \cdot \mathbf{U} \mathbf{N} \mathbf{B}\_{\mathbf{j}\mathbf{k}\mathbf{t}}^{\pm} \cdot \left( \mathbf{I} \mathbf{A} \mathbf{W}\_{\mathbf{j}\mathbf{k}\mathbf{t}}^{\pm} + \mathbf{R} \mathbf{W}\_{\mathbf{j}\mathbf{k}\mathbf{t}}^{\pm} \right) \tag{2b}$$

where j denotes the administrative region; k is the water use sectors (k = 1 for industry, k = 2 for municipal, k = 3 for agriculture, and k = 4 for the ecological environment); t is different periods in the planning horizon (t = 1 is phase I, t = 2 is phase II, and t = 3 is phase III); Lt is the length of period, which is fixed at 5 years; UNB± jkt represents water-use benefit (104 CNY/104 m3); IAW<sup>±</sup> jkt represents the initial allocation of water resources (10<sup>4</sup> <sup>m</sup>3/year); RW± jkt represents the reused water usage (104 <sup>m</sup>3/year).

(2) Ecological benefits:

$$\begin{array}{rcl} \mathbf{f}\_{2}^{\pm} =& \sum\_{\begin{subarray}{c} \mathbf{t} = 1 \ \mathbf{m} = 1 \\ \mathbf{t} = 1 \ \mathbf{m} = 1 \\ \mathbf{t} + \sum\end{subarray}} \sum\_{\begin{subarray}{c} \mathbf{L}\_{\mathbf{t}} \cdot \mathbf{L}\_{\mathbf{t}} \cdot \mathbf{A}\_{\mathbf{m} \mathbf{t}}^{\pm} + \sum\begin{subarray}{c} \mathbf{L}\_{\mathbf{t}} \cdot \mathbf{C}\_{2} \cdot \left(\sum\limits\_{m=1}^{4} \mathbf{A}\_{\mathbf{m} \mathbf{t}}^{\pm} \cdot \mathbf{D} + \sum\limits\_{n=1}^{24} \mathbf{S}\_{\mathbf{n} \mathbf{t}}^{\pm} \cdot \mathbf{Z}\right) \\ + \sum\limits\_{\mathbf{t} = 1}^{3} \sum\limits\_{m = 1}^{4} \mathbf{L}\_{\mathbf{t}} \cdot \mathbf{C}\_{2} \cdot \mathbf{A}\_{\mathbf{m} \mathbf{t}}^{\pm} \cdot \mathbf{V}\_{\mathbf{m} \mathbf{t}}^{\pm} + \sum\limits\_{\mathbf{t} = 1}^{3} \mathbf{L}\_{\mathbf{t}} \cdot \left(\sum\limits\_{m = 1}^{4} \mathbf{A}\_{\mathbf{m} \mathbf{t}}^{\pm} + \sum\limits\_{n = 1}^{24} \mathbf{S}\_{\mathbf{n} \mathbf{t}}^{\pm}\right) \cdot \mathbf{C}\_{3} \end{array} \tag{2c}$$

where m denotes types of wetland (m = 1–4 for riverine, coastal, marsh, and constructed wetlands, respectively), and n represents types of river (n = 1–24 for Biliu, Fuzhou, Dasha, Yingna, Zhuanghe, Huli, Diyin, Xiaosi, Geli, Zanzi, Qingshui, Anzi, Weitao, Yongning, Fudu, Langu, Dengsha, Sanshili, Shihe, Qingyun, Beida, Xiaogushan, Muchengyi, and Malan rivers, respectively). C1 is the scientific and cultural value of wetlands per m2, which is 0.382 CNY/m2. A<sup>±</sup> mt and S<sup>±</sup> nt denote wetland and river areas (104 m2), respectively. C2 represents the cost of the reservoir project, which is 0.67 CNY/m3. C3 is the value of wetland

and water body degrading pollution, taking 2.81 CNY/m2. Z represents the normal water level in the study region, which is 2.5 m. D is the maximum water storage difference, which is 2 m.

(3) Sectors of water shortage penalty:

$$\mathbf{f}\_3^{\pm} = \sum\_{\mathbf{j}=1}^6 \sum\_{\mathbf{k}=1}^3 \sum\_{\mathbf{t}=1}^3 \sum\_{\mathbf{h}=1}^3 \mathbf{L}\_{\mathbf{t}} \cdot \mathbf{p}\_{\mathbf{h}} \cdot \mathbf{P} \mathbf{N} \mathbf{B}\_{\mathbf{j}\mathbf{k}\mathbf{t}}^{\pm} \cdot \mathbf{D} \mathbf{W}\_{\mathbf{j}\mathbf{k}\mathbf{t}\mathbf{h}}^{\pm} \tag{2d}$$

where h represents various runoff scenarios in every period (h = 1 is low scenarios, h=2 is medium scenarios, h = 3 is high scenarios); Ph denotes the occurrence probability of scenario h; PNB± jkt represents the reduction of net benefit to sector k per unit of water resource not delivered (104 CNY/10<sup>4</sup> m3); DW<sup>±</sup> jkth is the allocation deficit of the surface water environment of Dalian that does not meet the initial water resource quotas of sector k during period t in region j under scenario h (104 m3/year).

(4) Penalty for lack of ecological water:

$$\mathbf{f}'^{\pm}\_{\ 3} = \sum\_{\mathbf{t}=1}^{3} \sum\_{\mathbf{h}=1}^{3} \mathbf{L}\_{\mathbf{t}} \cdot \mathbf{p}\_{\mathbf{h}} \cdot \left(\sum\_{\mathbf{m}=1}^{4} \mathbf{D} \mathbf{A}\_{\mathbf{m}\mathbf{t}}^{\pm} + \sum\_{\mathbf{n}=1}^{24} \mathbf{D} \mathbf{S}\_{\mathbf{n}\mathbf{t}}^{\pm}\right) \cdot \mathbf{P} \mathbf{N} \mathbf{A}\_{\mathbf{t}}^{\pm} \tag{2e}$$

where DA± mt and DS<sup>±</sup> nt represent the missing area of various types of wetlands and rivers that did not meet the ecological requirements during period t (104 m2/year). PNA<sup>±</sup> <sup>t</sup> is the water deficit loss in the ecosystem water department during period t (104 CNY/104 m2).

(5) Sectors of water supply cost:

$$\begin{array}{ll} \mathbf{f}\_{4}^{\pm} = & \sum\_{\mathbf{j}=1}^{6} \sum\_{\mathbf{k}=1}^{3} \sum\_{\mathbf{t}=1}^{3} \mathbf{L}\_{\mathbf{t}} \cdot \left( \mathbf{I} \mathbf{A} \mathbf{W}\_{\mathbf{j}\mathbf{k}\mathbf{t}}^{\pm} - \sum\_{\mathbf{h}=1}^{3} \mathbf{p}\_{\mathbf{h}} \cdot \mathbf{D} \mathbf{W}\_{\mathbf{j}\mathbf{k}\mathbf{t}\mathbf{h}}^{\pm} \right) \cdot \mathbf{C} \mathbf{W}\_{\mathbf{j}\mathbf{k}\mathbf{t}}^{\pm} \\ & + \sum\_{\mathbf{j}=1}^{6} \sum\_{\mathbf{k}=1}^{3} \sum\_{\mathbf{t}=1}^{3} \mathbf{L}\_{\mathbf{t}} \cdot \mathbf{R} \mathbf{W}\_{\mathbf{j}\mathbf{k}\mathbf{t}}^{\pm} \cdot \mathbf{C} \mathbf{R} \mathbf{W}\_{\mathbf{j}\mathbf{k}\mathbf{t}}^{\pm} \end{array} \tag{2f}$$

where CW± jkt represents the costs of water supply (10<sup>4</sup> CNY/10<sup>4</sup> <sup>m</sup>3); and CRW<sup>±</sup> jkt is the cost of reused water supply (104 CNY/104 m3).

(6) Ecological water use cost:

$$\mathbf{f}\_{4}^{\prime \pm} = \sum\_{\mathbf{t}=1}^{3} \mathbf{L}\_{\mathbf{t}} \cdot \left( \sum\_{\mathbf{m}=1}^{4} \left( \mathbf{A}\_{\mathbf{m}\mathbf{t}}^{\pm} - \mathbf{D} \mathbf{A}\_{\mathbf{m}\mathbf{t}}^{\pm} \right) + \sum\_{\mathbf{n}=1}^{24} \left( \mathbf{S}\_{\mathbf{n}\mathbf{t}}^{\pm} - \mathbf{D} \mathbf{S}\_{\mathbf{n}\mathbf{t}}^{\pm} \right) \right) \cdot \mathbf{S} \mathbf{C} \mathbf{W}\_{\mathbf{t}}^{\pm} \tag{2g}$$

where SCW± <sup>t</sup> is the cost of water resources in the eco-environmental water department in period t (104 CNY/104 m2).

(7) Wastewater treatment cost:

$$\mathbf{f}\_5^{\pm} = \sum\_{\mathbf{j}=1}^6 \sum\_{\mathbf{k}=1}^4 \sum\_{\mathbf{t}=1}^3 \mathbf{L\_t} \cdot \left( \begin{array}{c} \mathbf{IAW}\_{\mathbf{j}\mathbf{k}\mathbf{t}}^{\pm} - \sum\_{\mathbf{h}=1}^3 \mathbf{p\_h} \cdot \mathbf{DW}\_{\mathbf{j}\mathbf{k}\mathbf{th}}^{\pm} \\ + \mathbf{RW}\_{\mathbf{j}\mathbf{k}\mathbf{t}}^{\pm} \end{array} \right) \cdot \mathbf{c\_{jkt}} \cdot \mathbf{CWW}\_{\mathbf{j}\mathbf{k}\mathbf{t}}^{\pm} \tag{2h}$$

where CWW± jkt represents the costs of wastewater treatment (104 CNY/10<sup>4</sup> <sup>m</sup>3); and <sup>α</sup>jkt represents the wastewater emission coefficient.

Subject to:

(1) Water supply constraints:

$$\sum\_{\mathbf{k}=1}^{3} \left( \mathbf{IAW}\_{\mathbf{jkt}}^{\pm} - \mathbf{DW}\_{\mathbf{jkt}}^{\pm} \right) \le \mathbf{AWQ}\_{\mathbf{th}}^{\pm}; \forall \mathbf{t}, \mathbf{h} \tag{2i}$$

$$\rm{LW}^{\pm}\_{\rm jkth} \le \rm{LAW}^{\pm}\_{\rm jkt'} \forall \rm{j}, \rm{k}, \rm{t}, \rm{h} \tag{2j}$$

where AWQ± th represents available water resources in Dalian (104 <sup>m</sup>3/year).

(2) Demand constraints of water use sectors:

$$\rm{IAW^{\pm}\_{j\text{kt}} - DW^{\pm}\_{j\text{kth}} + RW^{\pm}\_{j\text{kt}} \ge WD^{\pm}\_{\text{min}}}\_{\text{min}}; \forall \text{j, k, t, h} \tag{2k}$$

$$\text{IAW}\_{\text{jkt}}^{\pm} - \text{DW}\_{\text{jkth}}^{\pm} + \text{RW}\_{\text{jkt}}^{\pm} \le \text{WD}\_{\text{max}}^{\pm} \, \_{\text{jkt}'} \forall \text{j}, \, \text{k}, \, \text{h} \tag{21}$$

where WD± minjkt and WD<sup>±</sup> maxjkt represent the minimum and maximum water resources requirement, respectively (104 m3/year).

(3) Regional wastewater treatment capacity constraints:

$$\sum\_{\mathbf{k}=1}^{2} \left( \mathbf{IAW}\_{\mathbf{jkt}}^{\pm} - \mathbf{DW}\_{\mathbf{jkt}}^{\pm} + \mathbf{RW}\_{\mathbf{jkt}}^{\pm} \right) \cdot \mathbf{z}\_{\mathbf{jkt}} \le \mathbf{ATW}\_{\mathbf{jkt'}}^{\pm} \,\forall \mathbf{j}, \mathbf{k}, \mathbf{t}, \mathbf{h} \tag{2m}$$

where ATW± jkt represents the wastewater treatment capacity (104 tons/year).

(4) Regional wastewater reuse capacity constraints:

$$\sum\_{\mathbf{k}=1}^{2} \left( \mathbf{IAW}\_{\mathbf{j}\mathbf{k}\mathbf{t}}^{\pm} - \mathbf{DW}\_{\mathbf{j}\mathbf{k}\mathbf{t}\mathbf{t}}^{\pm} + \mathbf{RW}\_{\mathbf{j}\mathbf{k}\mathbf{t}}^{\pm} \right) \cdot \mathbf{a}\_{\mathbf{j}\mathbf{k}\mathbf{t}} \cdot \boldsymbol{\xi}\_{\mathbf{j}\mathbf{k}\mathbf{t}} \geq \sum\_{\mathbf{k}=1}^{4} \mathbf{RW}\_{\mathbf{j}\mathbf{k}\mathbf{t}'}^{\pm} \,\forall \mathbf{j}, \mathbf{t} \tag{2n}$$

where ξjkt is the wastewater reuse rate.

(5) Water environmental carrying capacity constraint:

$$\sum\_{\mathbf{j}=1}^{6} \sum\_{\mathbf{k}=1}^{4} \left( \begin{array}{c} \text{IAW}\_{\text{jkt}}^{\pm} - \text{DW}\_{\text{jkth}}^{\pm} \\ + \text{RW}\_{\text{jkt}}^{\pm} \end{array} \right) \cdot \alpha\_{\mathbf{j}\text{kt}}^{\pm} \cdot \beta\_{\mathbf{j}\text{kt}}^{\pm} \cdot \text{EC}\_{\text{krt}}^{\pm} \cdot \text{IDR}\_{\text{krt}} \cdot \lambda\_{\mathbf{j}} \le \text{ALD}\_{\text{jrth}}^{\pm} \cdot \forall \mathbf{j}, \text{r.t.} \text{h} \tag{2o}$$

where r represents the type of pollutant (r = 1 for chemical oxygen demand (COD), r=2 for ammonia nitrogen (NH4-N), r = 3 for total phosphorus (Tp)); EC<sup>±</sup> krt represents the concentration of pollutant r after wastewater treatment (tons/10<sup>4</sup> m3); IDRkrt represents the river load ratio; βjkt is the wastewater concentration treatment coefficient; Xij is the receiving ratio of water; and ALD± irth represents the water environment carrying capacity (tons/year).

(6) Ecological value factor constraints:

$$\mathbf{A}\_{\mathbf{m}\mathbf{t}}^{\pm} - \mathbf{D} \mathbf{A}\_{\mathbf{m}\mathbf{t}}^{\pm} \ge \mathbf{P} \mathbf{R} \mathbf{A}\_{\mathbf{m}\mathbf{t}'}^{\pm} \,\forall \mathbf{m}, \mathbf{t} \tag{2p}$$

$$\rm{S}\_{\rm{nt}}^{\pm} - \rm{DS}\_{\rm{nt}}^{\pm} \ge \rm{PRS}\_{\rm{nt}\prime}^{\pm} \,\forall \mathbf{n}, \mathbf{t} \tag{2q}$$

$$\sum\_{\mathbf{m}=1}^{4} \left( \mathbf{A}\_{\mathbf{m}\mathbf{t}}^{\pm} - \mathbf{D} \mathbf{A}\_{\mathbf{m}\mathbf{t}}^{\pm} \right) \cdot \mathbf{V}\_{\mathbf{m}\mathbf{t}}^{\pm} + \sum\_{\mathbf{n}=1}^{24} \left( \mathbf{S}\_{\mathbf{n}\mathbf{t}}^{\pm} - \mathbf{D} \mathbf{S}\_{\mathbf{n}\mathbf{t}}^{\pm} \right) \cdot \mathbf{V}\_{\mathbf{n}\mathbf{t}}^{\pm} \le \mathbf{I} \mathbf{A} \mathbf{S}\_{\mathbf{t}}^{\pm} \; \forall \mathbf{t}, \mathbf{h} \tag{2r}$$

where V± mt and V<sup>±</sup> nt represent water storage capacity at normal water level (104 m3/104 m2), PRA± mt and PRS<sup>±</sup> nt, respectively, represent the minimum area of wetlands and rivers in the study area to ensure ecological functions (10<sup>4</sup> m2); and IAS<sup>±</sup> <sup>t</sup> represents the amount of water resources available in the ecological environment department (104 m3/year).

(7) Other:

$$\text{D} \text{W}\_{\text{jkth}'}^{\pm} \text{R} \text{W}\_{\text{jkt}'}^{\pm} \text{D} \text{A}\_{\text{mt}'}^{\pm} \text{D} \text{S}\_{\text{nt}}^{\pm} \ge 0 \tag{2s}$$

Using an interactive algorithm, the ITSP model can be transformed into two deterministic sub-models corresponding to the lower and upper bound values of the desired objective function. By solving the two sub-models, DW− jkth, DW<sup>+</sup> jkth,RW<sup>+</sup> jkt,RW<sup>−</sup> jkt, DA<sup>−</sup> mt, DA<sup>+</sup> mt, DS<sup>−</sup> nt, DS<sup>+</sup> nt were obtained, forming the final ITSP model as DW− jkth, DW<sup>+</sup> jkth , RW− jkt, RW<sup>+</sup> jkt , & DA− mt, DA<sup>+</sup> mt' , & DS− nt, DS<sup>+</sup> nt' .

#### *3.2. Model Parameters*

Table 1 lists the upper and lower bounds of the initial resource allocation of each water sector in Dalian. These were determined based on the latest last 10 years of regional water resource consumption in each sector and on the developmental planning for the region.


**Table 1.** Upper and lower bounds of the initial water resource allocation in Dalian (104 m3/year).

#### **4. Results and Discussion**

#### *4.1. Allocation of Water Resources in the Water Department*

Table 2 lists the initial optimal allocation of water resources in Dalian. It can be observed that the optimal allocation of water resources is close to the upper limit of the initial plan because more water allocation will bring more water resource benefits to various water-consuming sectors [24]. With the development of the society and economy, the annual water demand of the industrial and municipal domestic water sectors in different planning periods is gradually increasing. The development of Dalian is relatively balanced. Except for the ecological environment, the industrial water consumption in the study area accounts for about 43%, and the municipal and agricultural water consumption accounts for 32% and 25%, respectively.


**Table 2.** The initial optimal allocation of water resources in Dalian (104 m3/year).

Figures 4 and 5, respectively, show the amount of water reused by the industrial and municipal sectors in different planning periods. As shown in Figure 3, in regions Four Districts, Pulandian, and Zhuanghe, due to the higher water consumption rate and reclaimed water reuse rate of the industrial sector, the amount of reused water allocated gradually increased over time. For example, in region Zhuanghe, water reuse quotas were 27.02 × 104~54.37 × <sup>10</sup>4, 32.78 × <sup>10</sup>4~63.44 × <sup>10</sup>4, and 37.76 × <sup>10</sup>4~68.65 × <sup>10</sup><sup>4</sup> m3/year during the three periods. However, in regions Lvshunkou, Jinpu, and Wafangdian, water reuse quotas showed opposite trends for the three periods. The water reuse quotas were 18.80 × 104~38.93 × 104, 17.44 × 104~37.35 × 104, and 14.83 × 104~31.96 × 104 m3/year for region Lvshunkou; 4.36 × 104~5.97 × 104, 3.98 × 104~4.89 × 104, and3.14 × 104~4.74 × 104 m3/year for region Jinpu; 28.32 × <sup>10</sup>4~71.20 × 104, 24.06 × <sup>10</sup>4~56.33 × 104, and 19.04 × 104~44.66 × <sup>10</sup><sup>4</sup> <sup>m</sup>3/year for region Wafangdian, during the three periods, respectively. The first reason may be that the industrial sector has a relatively high water revenue; hence, the initial water quota in these two regions is close to the highest water demand, and there is no need for excess water resource allocation. The second is that increased water use means more wastewater is produced, which may exceed the existing wastewater treatment capacity. Therefore, under the condition of limited wastewater treatment capacity, a higher initial allocation of water resources will lead to water waste. As observed from Figure 5, the water reuse quota allocated to municipal life in the three planning periods was relatively small, especially in regions Lvshunkou and Jinpu. The reused water allocated to municipal sectors was even as low as 0.02 × <sup>10</sup><sup>4</sup> <sup>m</sup>3/year. This may be because the municipal living sector has low demand for water reuse and low revenue; therefore, water is more likely to be allocated to the industrial sector with higher revenue. Since agricultural irrigation has higher requirements for reused water, it also has higher requirements for reused water treatment technologies. However, due to lower returns than the industrial sector, this is not considered.

**Figure 4.** Reused water resource allocations for industry (104 m3/year).

**Figure 5.** Reused water resource allocations for municipal use (104 m3/year).

Tables 3–5 list the upper and lower bounds of water resource scarcity in the industrial, municipal, and agricultural sectors of each planning area during the three planning periods. As observed from the table, as the water resources increase, water shortages decrease. For example, in period 1, region Four Districts, water shortages of the industrial, municipal, and agricultural sectors in low, medium, and high water resource scenarios for the three periods were as follows: 311.02 × <sup>10</sup>4~320.57 × <sup>10</sup>4, 149.79 × 104~245.81 × 104, and 101.59 × 104~201.70 × 104 m3/year for the industrial sector; 4682.25 × 104~5695.01 × <sup>10</sup>4, 1489.38 × <sup>10</sup>4~5695.01 × <sup>10</sup>4, and 0.00~5695.01 × <sup>10</sup><sup>4</sup> <sup>m</sup>3/year for the municipal sector; 2.80 × <sup>10</sup>4~59.73 × <sup>10</sup>4, 0, and 0 m3/year for the agricultural sector. Although the industrial sector had the highest water efficiency, it consumed a lot of water. Therefore, as the planning period progressed, the demand and shortage for water continued to increase. The industrial sector in region Zhuanghe had the largest water shortage, for which

the shortage under different water resource scenarios was 11,092.97 × <sup>10</sup>4~12,848.82 × 104, 594.47 × <sup>10</sup>4~3126.95 × <sup>10</sup>4, and 0.00~3126.95 × 104 m3/year in period 1, 11,886.10 × 104~15,872.69 × 104, 382.03 × 104~3619.22 × 104, and 0.00~3619.22 × 104 m3/year in period 2, 11,852.15 × <sup>10</sup>4~12,879.20 × <sup>10</sup>4, 625.84 × <sup>10</sup>4~4879.20 × <sup>10</sup>4, and 0.00~4879.20 × <sup>10</sup><sup>4</sup> <sup>m</sup>3/year in period 3. This is because, with the advancement of the planning period, the industry in region Zhuanghe had continuously increased water demand and water shortage. However, the lack of water in some other regions and water-consuming sectors did not show this regularity. For example, in region Jinpu, the municipal sector showed a low water resource scenario, and the water shortage was 2125.84 × 104~3128.79 × 104, 1548.06 ×104~3552.92 ×104, and884.61 × 104~2087.49 × 104 m3/year in the three periods, respectively, showing a significant downward trend. This is because, under the current conditions of the development and utilization of water resources, over time, the water demand of various sectors has gradually increased, and the water safety of municipal sectors should be prioritized during the allocation of water resources.

**Table 3.** Upper and lower bounds of water resource deficit for each sector under different scenarios in period 1 (104 m3/year).


**Table 4.** Upper and lower bounds of water resource deficit for each sector under different scenarios in period 2 (104 m3/year).



#### **Table 4.** *Cont.*

**Table 5.** Upper and lower bounds of water resource deficit for each sector under different scenarios in period 3 (104 m3/year).


#### *4.2. Analysis of Ecological Value Factors*

4.2.1. Analysis of Water Distribution in the Ecological Environment Department

Table 6 lists the initial water use scenarios for ecological environment sector of the administrative districts in Dalian. It was observed that the water consumption of the environment sector in each planning period gradually increased. Region Pulandian had the largest environmental water consumption, which was 3581.54 × <sup>10</sup>4, 3787.75 × <sup>10</sup>4, and 3888.45 × <sup>10</sup><sup>4</sup> <sup>m</sup>3/year in the three periods, and the environmental water consumption increased each year. The first reason for this may be the increasing importance of the protection of the water environment, and the second may be the increasing benefits received by the ecological environment sector, which has prompted more water resources to be allocated to the ecological environment sector.


**Table 6.** The initial optimal allocation of water resources for ecological environment sector in Dalian (10<sup>4</sup> m3/year).

Figure 6 shows the amount of water reused by the ecological environment sector. As shown in the figure, over time, the reused water quota gradually increased. For example, in region Pulandian, the amount of water reused was 336.73 × <sup>10</sup>4~398.94 × <sup>10</sup>4, 361.97 × 104~427.80 × 104, and 408.96 × <sup>10</sup>4~483.08 × <sup>10</sup><sup>4</sup> <sup>m</sup>3/year in the three periods. The ecological environment sector had increasing benefits from water use and a high water demand; therefore, after all sectors reach the minimum water requirements, priority should be given to the allocation of more reused water to the ecological environment sector. Regions Four Districts and Lvshunkou showed relatively low water reuse. In region Four Districts, the amount of water reused was 57.92 × 104~71.21 × 104, 82.37 × 104~105.93 × 104, and 93.05 × 104~119.88 × <sup>10</sup><sup>4</sup> <sup>m</sup>3/year during the three periods. This may be due to the relatively low river runoff in regions Four Districts and Lvshunkou. In region Jinpu, there was a very small difference between periods 2 and 3 in the amount of reused water; 299.06 × 104~396.30 × 104 and 301.81 × 104~404.97 × 104 <sup>m</sup>3/year, respectively. The reason may be that during period 2 in region Jinpu, the amount of water reused was sufficient to meet the water requirements, and excessive allocation caused water waste.

**Figure 6.** Reused water resource allocations for environment.

Tables 7–9 list the upper and lower bounds of water resource deficit for the ecological environment sector under different scenarios. As observed from the table, as the water resources increased, the amount of water shortages in the ecological environment sector decreased. For example, during period 1 in region Zhuanghe, the water deficits under different scenarios were 1415.75 × 104~1753.54 × <sup>10</sup>4, 384.57 × 104~1753.34 × 104, and 0.00~153.54 × <sup>10</sup><sup>4</sup> <sup>m</sup>3/year. Under the high water resources scenario, except for region Pulandian, the water shortage of the ecological environment sector was 0, and the water shortage of the ecological environment sector in regions Four Districts and Lvshunkou were 0 under all water resource scenarios. This is because the quality of the water environment is closely related to the profitability of other sectors and ensuring the water consumption of the ecological environment sector is the basic prerequisite for economic development and the improvement of the quality of human life. This is in line with the objectives of China's 14th Five-Year Plan, which states that "we will adhere to the priority of ecology, promote ecological protection and economic development in a concerted manner, and create a beautiful China where people and nature live in harmony".

**Table 7.** Upper and lower bounds of water resource deficit for ecological environment sector under different scenarios in period 1.


**Table 8.** Upper and lower bounds of water resource deficit for ecological environment sector under different scenarios in period 2.


**Table 9.** Upper and lower bounds of water resource deficit for ecological environment sector under different scenarios in period 3.


4.2.2. Analysis of the Missing Area of the Aquatic Ecosystem

The regulation service value created by aquatic ecosystems has a great relationship with the area of various types of aquatic ecosystems. The lack of ecosystem area indicates the damage of the ecosystem and the lack of ecosystem value, which is not conducive to the development of the society and economy. Figures 7 and 8 show the area of water loss in the ecosystem (various wetlands and rivers) during the three periods. It was observed that the loss of ecosystem area gradually decreased over time, and the loss of some rivers reached 0. For example, the area of marsh wetland loss was 55.69 × 104~59.96 × <sup>10</sup>4, 37.04 × 104~44.11 × <sup>10</sup>4, and 20.08 × <sup>10</sup>4~30.24 × 104 <sup>m</sup><sup>2</sup> in the three periods, respectively. In rivers 7 and 14, the amount of river area missing is 0 in the three periods. There is no increase in the area loss over time, because the amount of water used to maintain the normal development and relative stability of the aquatic ecosystem continued to increase, which reduced the area loss.

**Figure 7.** Loss of water ecosystem (wetland) area (104 m2).

**Figure 8.** Loss of water ecosystem (river) area (104 m2).

4.2.3. Analysis of the Value of Ecological Regulation Services

The optimal allocation model of water resources coupled with ecological value factors takes profit maximization as the objective function. The projected profit primarily includes the use of water resources and the regulation service value of the water ecosystem. The average annual ecological regulation service value of the three periods is shown in Figure 9. After the implementation of the optimal allocation of water resources, the overall value of Dalian's water ecosystem regulation services was on the rise, from 980,900 × 104 CNY in period 1 to 999,700 × <sup>10</sup><sup>4</sup> CNY in period 3. The values of the four types of indicators all

grew steadily, with the highest proportion being the hydrological regulation value, which increased from 959,400 × <sup>10</sup><sup>4</sup> CNY in period 1 to 972,100 × <sup>10</sup><sup>4</sup> CNY in period 3. This may be due to the gradual increase in the amount of water resources available for the ecological environment sector, the basic functions of the ecosystem are safeguarded and show a trend towards gradual improvement. Water ecosystems are creating more and more value and are in better environmental condition.

**Figure 9.** Ecological regulation service value (104 CNY/year).
