(1)
Wang Xiujie Lian Jijian
Civil Engineering School of Tianjin University, Tianjin 300072, China.
E-mail:ljj＠public.tjuc.com.cn, Tel. +86-22-27406390
Abstract: In order to meet the water supply demand for the industry,agriculture and inhabitant’s life in Shenyang city, this paper deals with the hydrogeologic feature and object function of surface-water subsystem and the structure feature and input and output feature of the groundwater subsystem .So build the model of the surface water and groundwater co-regulation and calculate, then compare with three plannings and analyses retail the result .We choose the best one. So that the foundations are provided to utilize reasonably the surface-water and the groundwater in shenyang area.
Keywords: surface water reservoir, groundwater system, co-regulation model, water supplies groundwater level
1 INTRODUCTION
The surface-water and Groundwater co-regulation developed rapidly with the development of the modern industry agriculture and scientific technology because the global population is increasing so that the demand for the water quantity is growing, which cause the contradiction of the supply and the demand for water source. The surface-water and the groundwater co-regulation makes the utility of the whole water resource system optical by controlling the hydraulic factors of the surface-water and groundwater. Haimes et al (1974,1977) dissociate the surface water and the groundwater, and study the optimal management of distribution in the water use zones of surface water and the extracting in the water use zones in groundwater by using the dynamic and linear programming.H.J morel-seytowy and Tissa Illangsekave (1975,1984,1986) built the functional relation of the control decision variable, initial state and result state of river-groundwater by series of response function. At the same time, they studied the model of the river-groundwater co-regulation. In homeland, Xu Juanming et al (1985) first built the model of the surface water and the groundwater co-regulation in Qing Huangdao Shi River and manage. In this model, the groundwater is regarded as the concentrated parameter.
2 FEATURE OF THE SURFACE WATER SUBSYSTEM
Shifosi reservoir is a sole important control engineer in Main River of Liao river .Its task is the flood prevention and the water supply for Shenyang.It will be as an equalizing reservoir in the future. This reservoir is a plain reservoir, which retains water by river weir, big dike in the north of Shenyang, flood protection embankment of the both Liao riverbanks, tributary backwater dike and surrounding village dike. Its normal pool level is 47.0 meter and the maximum flooded area is 44.0 km2. Its design reservoir capacity is 1.187×108 m3.
The catchment area from Shifosi reservoir to the source is 1.655×105 km2, which is converged by east and west Liao River and their tributary. The mean annual net inflow volume is 11.937×108 m3. It has two features:
1. Annual distribution is not very average and main inflow is in July, October and September.The net inflow volume is 11.937×108 m3 which is per 80 of the annual inflow volume.
2. The overyear variation is obvious. The most net inflow is 40.711×108 m3 in 1964 and the least is only 0.357 ×108 m3 in 1982.The former is 114 times as much as the latter. So if Shifosi reservoir is used as the only water supply resource, the utilization rate is very low.
Shifosi reservoir is a plain reservoir which is built on the Quaternary system’s friable sedimentary layer. The elevations of the main dam and the big dike are 51.09 m and the most reservoir water level is 47.0 m. The river bed height mark of the dead water level at the main dam base is 38.3m.The river safety flood discharge Lower River of Shifosi is 5500 m3 /s. After the reservoir will be built, the flood control standard, which was once in 20 years now, is increased to once in 100 years. The peak flow is 8991m3 /s. As for the reservoir, the water is ungated from 1 st July to tenth September annual when there is no water surplus except overflow in river course. So the reservoir can’t supply water.
3 FEATURE OF GROUNDWATER SUBSYSTEM
In this region, the groundwater is the pore phreatic water or the pore micro-confined water in the Quaternary system’s friable sedimentary which is shallow (50 m under the earth surface). The water-bearing media is main the run-flood sand and the gravel in medium-upper Pleistocene series. In longitudinal direction, the particle size turns coarser and coarser from upper the bottom. The top is medium-fine sand. The middle and the low are coarse sand and sandy gravel whose general thickness is from 17 m to 30 m. Near the Liao River, the thickness grows thicker and the most thickness is 42 m. From Liao River to its bilateral region.the thickness turns thin. In transverse direction, from Liao River to east west both sides the particle size of the water-bearing media gets more and more fine. The top of the most part of the water-bearing system is a layer of the subsand soil and the loam whose thickness is general from 1 to 10 m. Near Liao River, the layer gets thin or is deficient .So the groundwaters of the region is phreatic or shallow confined. The permeability coefficient of this aquifer is from 20 to 90 m/d. The average is 53.4 m /d. The unit water boil volume is from 600 to 2400 m3 /d.m.
The input types of the groundwater system are natural input and artificial input. The former includes the precipitation infiltration, evaporation, influent seepage recharge and discharge of the river channel, inflow and outflow of the lateral runoff. The latter includes extracting groundwater for industry agriculture and the infiltration of the irrigation water.
The groundwater levels as a kind of output form exits two peak values every year. The first peak value appears in August and September when the rainfall infiltration is strong. The second peak value which is less than the first one appears in February and May when the snow water infiltrates to recharge the groundwater. The hysteresis period of the groundwater infiltration responding is general from several days to a month. The minimum level appears in from May to July every year when the vertical infiltration is very small because under the artificial extracting groundwater and the evaluation discharge, the groundwater is in the dissipation. The annual range of the ground is general from 0.5 to 0.3 m and the annual range of the central extracting region is from 8 to 9 m.
4 THE CO-REGULATION MODEL
In the light of the total demand for the design planning on Shufosi reservoir, we should consider three rules as followed:
(1) Make full use of surface-water; discrease possibly the reservoir surplus.
(2) Utilize the interference wells and the regulation function of aquifer space and sure the aquifer not to be unwatered locally.
(3) Under the premise of not causing to submerge the reservoir, first utilize the surface-water (the embedded depth of the water level doesn’t reach 1 meter as the immersion standard)
4.1 Building of co-regulation water volume model
Shifosi reservoir keeps the close hydraulic relation to the groundwater in aquifer out of the reservoir by the permeable layer under dam (or dike) and the low water-bearing of the reservoir bottom. The reservoir leakage supplies the aquifer. The variation of the reservoir level effects the leakage. At the same time, the extracting volume of the interference wells out of the dike determines the variation of the groundwater in aquifer out of the reservoir. They effect each other. Under the regular structure of the groundwater system, the variation of the reservoir level and the groundwater determines the exchange quantity of the surface water reservoir and the groundwater reservoir by which the surface-water and the groundwater level are united a system. The reservoir level and the groundwater level are time function, so the surface-water reservoir and the groundwater reservoir must be built the united model and coupled by the both exchange water volume .The united models as followed:
(1)
(2)
(3)
where:
Sv+1=the reservoir storage of time v+1; Sv=the reservoir storage of time v; Iv+1=the reservoir precipitation recharge of time v+1；Pv+1=the reservoir net inflow of time v+1；Rv+1=the reservoir supply of time v+1；Ev+1=the reservoir evaporation of time v+1；Lv+1=the reservoir infiltration loss of time v+1；OUTv+1=the reservoir surplus water of time v+1；Hv+1=the reservoir water level of time v+1；Hiv+1=the groundwater level of time v+1 and nodal point i；kβ,mβ=the permeability coefficient k and the thickness m of the aquifer in the parameter area of the nodal point； kiβ,miβ=the permeability coefficient k and the thickness m of the top of the low permeable layer of the nodal point β；b=half of the dam or the width of the dam bottom；ηi=the length of the i dike and twice of the curtain；фnβ(xn,yn) =area coordinate；kij,kik=the harmonic average value of the permeability coefficient between node ij and node ik；ki, kj, kk=separate permeability coefficient of node i,node j and node k；μβ=water supply degree in the triangle of the water-table aquifer；wβ=vertical net evaporation intensity in the triangle；Zij=floor height mark of the water-table aquifer between node I and node j；Qn=the extracting of no nodal wells in coordinate (xn,yn)；Qi=the extracting of nodal wells i；Δβ=triangle area β；Δt=the length of time (day)；p=number of the triangle whose apex is node i；(xi,yi), (xj,yj), (xk,yk) =coordinate of node i,j,k(meter)；
Equation (1) is the dynamic model of the surface-water reservoir. Equation (3) is the dynamic model of the groundwater reservoir. Equation (2) is the water exchange equation of the groundwater and the surface-water. Three equations formed the united regulating model and solve jointly
4.2 Solution of the model
In the joint water quantity model, the surface water dynamic model is the linear equation in which the net inflow is known and the other is unknown. But the latter is relate to the reservoir capacity of each time interval which is the function of the reservoir water level which is solved. The groundwater model is a large non-linear equation group and can’t solve directly. So for the groundwater model, we use the over relaxation iteration method and for the surface water, we use Seder iteration method(Fig.1).
Fig.1 Chart of the calculated programming of
the groundwater and surface water
5 ALCULATED RESULT ANALYSIS
5.1 Calculated result analysis of the chosen scheme
According to the reservoir net inflow, time distribution, aquifer structure, and extracting condition of the groundwater, the chosen water supply are respecteve 70×104 m3/d, 72×104m3/dand 60×104 m3 per day, then calculate by long time series. In order to make the water supply steady, the planning of the 70×104 m3/d is adopted. The result of three water supply planning as followed:
Table1 Comparison of the result of three utilizing water
|
Water supply capacity (×105 t/d) |
60 |
70 |
72 |
|
Net inflow of the reservoir(×108t/a) |
12.171 |
12.171 |
12.171 |
|
Industrial use of water from the reservoir(×105 t/d) |
133.8 |
110.0 |
103.3 |
|
Evaporation loss(×105 t/d) |
9.5 |
7.0 |
6.2 |
|
Infiltration loss(×105 t/d) |
70.3 |
131.9 |
150.3 |
|
Surplus water from the reservoir(×105 t/d) |
957.0 |
968.2 |
957.0 |
|
Industrial use of water from the groundwater(×105 t/d) |
85.2 |
145.5 |
159.3 |
|
Years of the immersion (year) |
16 |
2 |
1 |
|
Maximum drawdown (m) |
14.3 |
19.4 |
22.4 |
|
Average drawdown (m) |
6.0 |
11.3 |
13.2 |
According to the water supply of the chosen 70×104 m3 which is the sum of the groundwater and the surface-water, we obtain the calculated result of the reservoir regulation and the groundwater balance in each time interval every year by operating 864 time intervals together 36 years on the computer.
5.2 Annual surface water balance
The overyear average inflow of the reservoir is 12.171×108 m3. The overyear average surface-water supply is 1.100×108 m3 (30×104 m3/d) which are per 43 of the total industrial use of weter. The overyear average groundwater supply is 1.461×108 m3 (40×104 m3 /d) which occupies per 57 of the total industrial use of water, The reservoir evaporation loss is 0.07×108 m3 and the infiltration loss is 1.319×108 m3 of which 0.202×108 m3 is the dam base infiltration loss, of which 1.17×108 m3 loss supplies the groundwater. The reservoir surplus water is 9.682×108m3 which is per 79.55 of the total inflows. Per 77 of the extracting of the groundwater comes from the recharge of the reservoir.
5.3 Annual groundwater balance
The overyear average lateral recharge is 0.164×108 m3. The vertical recharge is 1.223×108 m3and the reservoir water recharge is 1.319×108 m3. So the total recharge is 2.706 x108 m3. The lateral discharge is 0.041×108 m3. The vertical discharge is 0.35×108 m3. The river discharge is 0.0367×108 m3. The origin extracting is 0.598×108 m3. The new increment of extracting is 1.461×108 m3. The total discharge is 2.481×108 m3. So the overyear average balance is 0.219×108 m3.
For the balance of the groundwater, we choose three typical years to analyze. In high flow year, the total recharge is 3.334×108 m3 of which the surface-water recharge is 1.662×108 m3 which is per 49.9 of the total recharge. The total loss is 2.007×108 m3 .The former is more than the latter and the positive balance is 1.32×108 m3 which makes the water level lift. In normal year, the total recharge is 3.191×108 m3 of which the surface-water recharge is 1.799×108 m3 which occupies per 55.7 of the total recharge. The total loss is 2.647×108 m3. The both balance basically. The positive balance is 0.546×108 m3, which cause water level lift slightly. The groundwater appears the positive balance. In low year, the total recharge is 1.302×108 m3of which surface-water recharge is 0.271×108 m3 .The total loss is 3.084×108 m3. So the former is less than the latter, which makes the groundwater system appears negative balance whose value is 1.782×108 m3. So the groundwater level drops.
5.4 Result analysis
Under the daily water supply 75×104 m3, the average surface-water is 30×104 m3 /d and the groundwater is 40×104 m3, we may obtain the rules of the surface-water level and groundwater level of 864 time intervals in 36 years. The maximum value of the groundwater level appears in 2022 which is a high flow year. Except that the drawdown of the groundwater level, which is the upper reaches off the reservoir bottom, is no more than 1.0 m, other is more than 1.0 m. So it will not appear immersion of near area of the reservoir by operating this planning. The average drawdown depth of the groundwater level is 8.4 m which is third-one of the average thickness of aquifer. So the surplus depth is 15 m, which will not effect the operation of water pumps, what is more, the aquifer is not unwatered which meets the general co-regulation principle. The general variable rule of water level: Because in low year, the part storage of the groundwater system is used, the water level falls. The groundwater obtains recharge in high flow year of season, so the groundwater level rises again. From the overyear variation of water level, the groundwater system is basic in dynamic equilibrium. So we see, the planning operation of 70×104 m3 will not destroys the ground Water equilibrium and cause the region water level to fall,also not appears immersion, which brings into full play the storage action.
Fig.2 Joint water supply scale surface-water
and groundwater in 2022
The distribution water supply scale the three high, normal, and low years as followed.
6 CONCLUSIONS
The surface water and groundwater co-regulation can supply water of 70×104 m3 /d for ShenYang which is reasonable under the several calculation plannings. The co-regulation will not cause the around large mass immerse. The overyear average groundwater is 40 ×104 m3/d which is the extra extracting on base of the present industrial and agricultural extracting. The most part of the extra extracting comes from the loss of the reservoir of the river, which raise the utilization coefficient of the surface water. The reservoir infiltration in the normal year is 1.779×108 m3 which is per 80 of the extra pumping. So the co-regulation of the surface water and the ground water will not effect the present water supply .In a word, this example proves the availability of the surface water and the ground water co-regulation.
Fig.3 Joint water supply scale of
surface water and groundwater in 2007
Fig.4 Joint water supply scale of
surface-water and groundwater in
2018
References
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