RUNOFF YIELD CALCULATION METHOD AND DEVICE BASED ON DOUBLE FREE RESERVOIRS, AND STORAGE MEDIUM

Abstract

A runoff yield calculation method and device based on double free reservoirs, and a storage medium are provided, the method includes: forming a four-layer vadose zone structure by making a tension water storage layer be located under a deep vadose zone based on a three-layer vadose zone structure of a Xin'anjiang model; dividing a space occupied by free water in the four-layer vadose zone structure into an upper free reservoir and a lower free reservoir; calculating a time interval runoff yield by using a saturation excess runoff method; and dividing, based on a runoff yield structure of the double free reservoirs, the time interval runoff yield into a surface runoff, an interflow and a subsurface runoff. The method proposes a runoff yield structure of double free reservoirs, which can be well applied to semi-arid and semi humid watersheds with deeper buried depth of shallow groundwater.

Claims

1. A runoff yield calculation method based on double free reservoirs, comprising: building a runoff yield structure of the double free reservoirs, comprising: forming a four-layer vadose zone structure comprising an upper vadose zone, a lower vadose zone, a deep vadose zone and a tension water storage layer by making the tension water storage layer be located under the deep vadose zone based on a three-layer vadose zone structure of a Xin'anjiang model; and dividing a space occupied by free water in the four-layer vadose zone structure into an upper free reservoir and a lower free reservoir; wherein the upper vadose zone, the lower vadose zone and the deep vadose zone occupy the upper free reservoir, and the tension water storage layer occupies the lower free reservoir; calculating a time interval runoff yield by using a saturation excess runoff method; and dividing and calculating, based on the runoff yield structure of the double free reservoirs, the time interval runoff yield into three runoff components comprising: a surface runoff, an interflow and a subsurface runoff.

2. The runoff yield calculation method according to claim 1, wherein calculation formulas for the calculating, based on the runoff yield structure of the double free reservoirs, the surface runoff, the interflow and the subsurface runoff are as follows: $R_s\left(t\right)=\{\begin{array}{cc}0,& R\left(t\right)+S\left(t\right)\le S_M\\ R\left(t\right)+S\left(t\right)-S_M,& R\left(t\right)+S\left(t\right)>S_M\end{array};$ where R.sub.s(t) represents the surface runoff at a t time interval, S.sub.M represents an upper free water storage capacity, R(t) represents the time interval runoff yield at the t time interval, and S(t) represents a water storage of the upper free reservoir at beginning of the t time interval;
R.sub.i(t)=K.sub.i*(R(t)+S(t)−R.sub.s(t)−F.sub.d(t)); where R.sub.i(t) represents the interflow at the t time interval, K.sub.i represents an outflow coefficient of the interflow, and F.sub.d(t) represents an inflow of the lower free reservoir at the t time interval; $R_{ℊ}\left(t\right)=\{\begin{array}{cc}0,& F_d\left(t\right)+S_l\left(t\right)\le S_{\mathrm{LM}}\\ K_{ℊ}*\left(F_d\left(t\right)+S_l\left(t\right)-S_{\mathrm{LM}}\right),& F_d\left(t\right)+S_l\left(t\right)>S_{\mathrm{LM}}\end{array};$ where R.sub.g(t) represents the subsurface runoff at the t time interval, S.sub.l(t) represents a water storage of the lower free reservoir at beginning of the t time interval, S.sub.LM represents a lower free water storage capacity, and K.sub.g represents an outflow coefficient of the subsurface runoff.

3. The runoff yield calculation method according to claim 2, wherein a calculation formula for the time interval runoff yield R(t) at the t time interval is as follows: $R\left(t\right)=\{\begin{array}{cc}0,& P_{\epsilon }\left(t\right)\le 0\mathrm{or}{P}_{\epsilon }\left(t\right)+W\left(t\right)\le W_M\\ P_{\epsilon }\left(t\right)+W\left(t\right)-W_M,& P_{\epsilon }\left(t\right)+W\left(t\right)>W_M\end{array};$ where W(t) represents a tension water storage at an initial time of the t time interval; W.sub.M represents a tension water storage capacity, and P.sub.ε(t) represents a time interval net rainfall at the t time interval after deducting evapotranspiration loss and vegetation canopy interception loss.

4. The runoff yield calculation method according to claim 2, wherein a calculation formula for the water storage S(t) of the upper free reservoir at beginning of the t time interval is as follows: $S\left(t\right)=\{\begin{array}{cc}S\left(t-1\right)+R\left(t-1\right)-R_i\left(t-1\right)-R_s\left(t-1\right)-F_d\left(t-1\right),& t>1\\ S\left(0\right),& t=1\end{array};$ where S(t−1) represents the water storage of the upper free reservoir at a (t−1) time interval, R(t−1) represents the time interval runoff yield at the (t−1) time interval, R.sub.i(t−1) represents the interflow at the (t−1) time interval, R.sub.s(t−1) represents the subsurface runoff at the (t−1) time interval, F.sub.d(t−1) represent the inflow of the lower free reservoir at the (t−1) time interval, and S(0) represents the storage capacity of the upper free reservoir at an initial time, which is set according to one of an initial state observed value and an estimated value of a watershed.

5. The runoff yield calculation method according to claim 2, wherein a calculation formula for the inflow F.sub.d(t) of the lower free reservoir at the t time interval is as follows: $F_d\left(t\right)=\min \left(R\left(t\right)+S\left(t\right)-R_i\left(t\right)-R_s\left(t\right),K\left(1+\frac{\Psi \mathrm{\Delta \theta }}{F\left(t\right)}\right)\right);$ where K represents a soil saturated hydraulic conductivity, Ψ represents a soil suction at wetting front, Δθ represents a difference between a soil saturated moisture content and a field water capacity, and F(t) represents a cumulative leakage at beginning of the t time interval.

6. The runoff yield calculation method according to claim 5, wherein a calculation formula for the cumulative leakage F(t) at beginning of the t time interval is as follows: $F\left(t\right)=\{\begin{array}{cc}{.Math.}_{i=t-300}^{t-1}{F}_d\left(i\right)+F_0,& t>300\\ {.Math.}_{i=1}^{t-1}{F}_d\left(i\right)+F_0,& t>1\\ F_0,& t=1\end{array};$ where F.sub.d(i) represents the inflow of the lower free reservoir at an i time interval, and F.sub.0 represents a leakage at an initial time.

7. The runoff yield calculation method according to claim 2, wherein calculation formulas for the water storage S.sub.l(t) of the lower free reservoir at beginning of the t time interval and the lower free water storage capacity S.sub.LM are as follows: $S_l\left(t\right)=\{\begin{array}{cc}{S}_l\left(t-1\right)+F_d\left(t-1\right)-R_{ℊ}\left(t-1\right),& t>1\\ S_l\left(0\right),& t=1\end{array};$ $S_{\mathrm{LM}}=\{\begin{array}{cc}\left(Z_r-Z_{ℊ}\right)*\mu ,& Z_r>Z_{ℊ}>Z_i\\ \left(Z_r-Z_i\right)*\mu ,& Z_r>Z_i\ge Z_{ℊ}\\ 0,& Z_{ℊ}\ge Z_r\end{array};$ where S.sub.l(0) represents the water storage of the lower free reservoir at an initial time, Z.sub.r represents a river level elevation at the initial time, Z.sub.g represents a groundwater level elevation at the initial time, Z.sub.i represents a bottom boundary elevation of an aquifer underlying a river channel, μ represents a specific yield of a groundwater level fluctuation zone, and S.sub.l(0), Z.sub.r, and Z.sub.g are set according to initial state observation values or estimated values of a watershed.

8. A runoff yield calculation device, comprising a processor and a memory, wherein the memory is stored with programs or instructions, and the processor is configured to, when the programs or the instructions are loaded and executed by the processer, implement the runoff yield calculation method according to claim 1.

9. A non-transitory computer-readable storage medium stored with programs or instructions, wherein the programs or the instructions are executable by a processor to implement the runoff yield calculation method according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG. 1 illustrates a schematic flowchart of a runoff yield calculation method based on double free reservoirs provided by the disclosure.

[0022] FIG. 2 illustrates a schematic structural diagram of a runoff yield structure of double free reservoirs provided by the disclosure.

[0023] FIG. 3 illustrates a comparison diagram of flood simulation performance of a runoff yield calculation method based on double free reservoirs provided by the disclosure and a runoff yield calculation method based on single free reservoir provided by the related art.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The disclosure is further described below in combination with the accompanying drawings and specific embodiments.

[0025] It should be understood that the specific embodiments described herein are only used to explain the disclosure and are not used to define the disclosure.

Embodiment 1

[0026] As illustrated in FIG. 1, the embodiment of the disclosure provides a runoff yield calculation method based on double free reservoirs, including the step 1 to the step 3.

[0027] At the step 1, building a runoff yield structure of the double free reservoirs.

[0028] A schematic structural diagram of the runoff yield structure of the double free reservoirs as illustrated in FIG. 2. The step S1 includes forming a four-layer vadose zone structure including an upper vadose zone, a lower vadose zone, a deep vadose zone and a tension water storage layer by making the tension water storage layer be located under the deep vadose zone based on a three-layer vadose zone structure of a Xin'anjiang model; and dividing a space occupied by free water in the vadose zone (also referred to as four-layer vadose zone structure) into an upper free reservoir and a lower free reservoir, in which the upper vadose zone, the lower vadose zone and the deep vadose zone occupy the upper free reservoir, and the tension water storage layer occupies the lower free reservoir.

[0029] At the step 2, calculating a time interval runoff yield by using a saturation excess runoff method by using formula (1), and obtaining a time interval net rainfall after deducting evapotranspiration loss and vegetation canopy interception loss.

[00008]$\begin{array}{cc}R\left(t\right)=\{\begin{array}{cc}0,& P_{\epsilon }\left(t\right)\le 0\mathrm{or}{P}_{\epsilon }\left(t\right)+W\left(t\right)\le W_M\\ P_{\epsilon }\left(t\right)+W\left(t\right)-W_M,& P_{\epsilon }\left(t\right)+W\left(t\right)>W_M\end{array};& \mathrm{Formula}\left(1\right)\end{array}$

[0030] where R(t) represents the time interval runoff yield at a t time interval, W(t) represents a tension water storage at an initial time of the t time interval; W.sub.M represents a tension water storage capacity, and P.sub.ε(t) represents a time interval net rainfall at the t time interval after deducting evapotranspiration loss and vegetation canopy interception loss.

[0031] At the step 3, dividing, based on the built runoff yield structure of the double free reservoirs, the time interval runoff yield into three runoff components including: a surface runoff, an interflow and a subsurface runoff by using formulas (2) to (9); and simulating a runoff yield process of a watershed in a semi-arid and semi-humid area according to the surface runoff, the interflow and the subsurface runoff.

[00009]$\begin{array}{cc}{R}_s\left(t\right)=\{\begin{array}{cc}0,& R\left(t\right)+S\left(t\right)\le S_M\\ R\left(t\right)+S\left(t\right)-S_M,& R\left(t\right)+S\left(t\right)>S_M\end{array};& \mathrm{Formula}\left(2\right)\end{array}$

[0032] where R.sub.s(t) represents the surface runoff at a t time interval, R(t) represents the time interval runoff yield at the t time interval, S(t) represents a water storage of the upper free reservoir at beginning of the t time interval, and S.sub.M represents an upper free water storage capacity.

[0033] Calculating R.sub.i(t) and S(t) by using formula (3) and formula (4):

[00010]$\begin{array}{cc}{R}_i\left(t\right)=K_i*\left(R\left(t\right)+S\left(t\right)-R_s\left(t\right)-F_d\left(t\right)\right);& \mathrm{Formula}\left(3\right)\end{array}$$\begin{array}{cc}S\left(t\right)=\{\begin{array}{cc}S\left(t-1\right)+R\left(t-1\right)-R_i\left(t-1\right)-R_s\left(t-1\right)-F_d\left(t-1\right),& t>1\\ S\left(0\right),& t=1\end{array};& \mathrm{Formula}\left(4\right)\end{array}$

[0034] where R.sub.i(t) represents the interflow at the t time interval, K.sub.i represents an outflow coefficient of the interflow, and F.sub.d(t) represents an inflow of the lower free reservoir at the t time interval; S(t−1) represents the water storage of the upper free reservoir at a (t−1) time interval, R(t−1) represents the time interval runoff yield at the (t−1) time interval, R.sub.i(t−1) represents the interflow at the (t−1) time interval, R.sub.s(t−1) represents the subsurface runoff at the (t−1) time interval, F.sub.d(t−1) represent the inflow of the lower free reservoir at the (t−1) time interval, and S(0) represents the storage capacity of the upper free reservoir at an initial time, which is set according to one of an initial state observed value and an estimated value of a watershed.

[00011]$\begin{array}{cc}{F}_d\left(t\right)=\min \left(R\left(t\right)+S\left(t\right)-R_i\left(t\right)-R_s\left(t\right),K\left(1+\frac{\Psi \mathrm{\Delta \theta }}{F\left(t\right)}\right)\right);& \mathrm{Formula}\left(5\right)\end{array}$

[0035] where K represents a soil saturated hydraulic conductivity, Ψ represents a soil suction at wetting front, Δθ represents a difference between a soil saturated moisture content and a field water capacity, and F(t) represents a cumulative leakage at beginning of the t time interval.

[00012]$\begin{array}{cc}F\left(t\right)=\{\begin{array}{cc}{.Math.}_{i=t-300}^{t-1}{F}_d\left(i\right)+F_0,& t>300\\ {.Math.}_{i=1}^{t-1}{F}_d\left(i\right)+F_0,& t>1\\ F_0,& t=1\end{array};& \mathrm{Formula}\left(6\right)\end{array}$

[0036] where F.sub.d(i) represents the inflow of the lower free reservoir at an i time interval, and F.sub.0 represents a leakage at an initial time of rainfall, which can be set to a minimum value, such as 0.001.

[00013]$\begin{array}{cc}{R}_{ℊ}\left(t\right)=\{\begin{array}{cc}0,& F_d\left(t\right)+S_l\left(t\right)\le S_{\mathrm{LM}}\\ K_{ℊ}*\left(F_d\left(t\right)+S_l\left(t\right)-S_{\mathrm{LM}}\right),& F_d\left(t\right)+S_l\left(t\right)>S_{\mathrm{LM}}\end{array};& \mathrm{Formula}\left(7\right)\end{array}$

[0037] where R.sub.g(t) represents the subsurface runoff at the t time interval, S.sub.l(t) represents a water storage of the lower free reservoir at beginning of the t time interval, S.sub.LM represents a lower free water storage capacity, and K.sub.g represents an outflow coefficient of the subsurface runoff

[0038] In the step 3, calculation formulas for the water storage of the lower free reservoir and the lower free water storage capacity are as shown as formula (8) and formula (9):

[00014]$\begin{array}{cc}{S}_l\left(t\right)=\{\begin{array}{cc}{S}_l\left(t-1\right)+F_d\left(t-1\right)-R_{ℊ}\left(t-1\right),& t>1\\ S_l\left(0\right),& t=1\end{array};& \mathrm{Formula}\left(8\right)\end{array}$$\begin{array}{cc}{S}_{\mathrm{LM}}=\{\begin{array}{cc}\left(Z_r-Z_{ℊ}\right)*\mu ,& Z_r>Z_{ℊ}>Z_i\\ \left(Z_r-Z_i\right)*\mu ,& Z_r>Z_i\ge Z_{ℊ}\\ 0,& Z_{ℊ}\ge Z_r\end{array};& \mathrm{Formula}\left(9\right)\end{array}$

[0039] where S.sub.l(0) represents the water storage of the lower free reservoir at an initial time, Z.sub.r represents a river level elevation at the initial time, Z.sub.g represents a groundwater level elevation at the initial time, Z.sub.i represents a bottom boundary elevation of an aquifer underlying a river channel, μ represents a specific yield of a groundwater level fluctuation zone, and the above state variable values at the initial time are set according to initial state observation values or estimated values of the watershed.

[0040] The Qingshui River watershed in the Haihe River watershed in the typical semi-arid and semi-humid area is selected as an implementation object. The runoff yield calculation method based on double free reservoirs provided by the disclosure and the runoff yield calculation method based on single free reservoir provided by the related art are used to calculate the corresponding three runoff components under the two different runoff yield algorithms, and a unified concentration algorithm is used to calculate the runoff concentration (the slope and river network concentration adopt the muskingen algorithm). Through parameter optimization and adjustment, the optimal flood simulation performance of the two algorithms is obtained. Referring to “Hydrological information forecast specification GB/T 22482-2008”, a peak discharge relative error, a peak time error, a Nash-Sutcliffe efficiency coefficient and a runoff depth error are selected as evaluation indicators. It can be found that the simulation performance of the runoff yield calculation method based on the double free reservoirs is better than the runoff yield calculation method based on the single free reservoir, as illustrated in FIG. 3.

Embodiment 2

[0041] The disclosure provides a device, configured to calculate runoff yield. The device includes a processor and a memory, the memory is stored with programs or instructions, and the programs or the instructions are loaded and executed by the processor to implement the runoff yield calculation method according to the embodiment 1.

Embodiment 3

[0042] The disclosure provides a computer-readable storage medium. The computer-readable storage medium can be a non-transitory computer-readable storage medium; or the computer-readable storage medium can be a volatile computer-readable storage medium. The computer-readable storage medium is stored with instructions, when the instructions are running on a computer, the computer can implement the runoff yield calculation method according to the embodiment 1. Specifically, the instructions are executable by a processor to implement the runoff yield calculation method according to the embodiment 1.

[0043] Those skilled in the art can clearly understand that the technical solutions of the disclosure, in essence, or the part that contributes to the related art, or all or part of the technical solutions, can be embodied in the form of a software product, which is stored in a storage medium, it includes instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in various embodiments of the disclosure. The storage media include: U disk, mobile hard disk, read only memory (ROM), random access memory (RAM), magnetic disc or optical disc and other media that can store program codes.

[0044] The above are only the illustrated embodiments of the disclosure, and are not used to define the disclosure. Those skilled in the art make several amendments and optimizations without departing from the concept of the disclosure, which should be regarded as the protection scope of the disclosure.