Calculation method for water conservation amount

Abstract

The invention discloses a water conservation amount calculation method which is characterized by comprising the following steps: step 1, hydrogen and oxygen isotope determination, step 2, wave function simulation and period estimation, and step 3, watershed water source oxygen content estimation. The invention provides a method for revealing a tree moisture source and a drainage basin moisture source by means of an isotope tracing method, the average retention time of the drainage basin moisture is estimated according to the seasonal change, the length of the drainage basin moisture transportation process is reflected, the water conservation capacity and the total amount are also reflected, and a method for determining the moisture content of the drainage basin by means of the hydrogen and oxygen isotope tracing technology is provided. Therefore, the understanding of water conservation is expanded, namely, the technical path of deeply understanding the water conservation effect from the estimation of the quantity to the common understanding of the quantity and the effect is expanded.

Description

Technical Field

[0001] The invention relates to the technical field of hydrological technical analysis, and in particular to a method for calculating water conservation capacity. Background Art

[0002] Water conservation is fundamentally the process and ability of an ecosystem to retain water within a certain time and space. Due to factors such as the history of scientific development and differences in the understanding of connotations, "water conservation" is a special term in the Chinese context. In terms of connotation, water conservation in the Chinese context not only includes water storage, but also implies the "protection" and "cultivation" of water or water resources, that is, "conservation" and "nurturing", and its possible derived functions, such as groundwater recharge, regulation of river flow, water purification and other ecosystem functions. Therefore, water conservation is not only a key link in the water cycle of the ecosystem and an important link in the material cycle, but also one of the important ecological services of the ecosystem.

[0003] The calculation methods of water conservation capacity include: water balance, stratified water storage, precipitation storage, model simulation, satellite remote sensing and other methods. The water balance method calculates the conservation capacity by subtracting the output water from the system input water. The water storage estimation method estimates the conservation capacity by quantifying the canopy interception, litter water holding capacity and soil pore water storage, and then summing them up. The precipitation storage method estimates the conservation water based on the difference in runoff coefficients between the study land type (such as woodland, grassland) and the control land type (bare land). Model simulation mainly relies on mature hydrological models, such as SWAT, to simulate ecosystem water resource supply services; satellite remote sensing is more suitable for large-scale water resource assessment.

[0004] Due to the different estimation mechanisms, the applicability of these methods varies. For example, the water balance method and precipitation storage method are simple and clear, suitable for large-scale studies with small spatial heterogeneity or ignoring spatial effects. The water storage estimation method is relatively clear, and soil moisture dynamic monitoring can directly monitor the change process of soil moisture, but this method ignores the interaction and connection between systems (such as between soil and plants). The water storage carrier of the basin is not limited to the soil layer, canopy or litter layer, and the rock weathering layer also plays an important role in water storage. Moreover, all existing methods do not take into account the impact of the complex ecological processes of the "soil-plant-atmosphere" system, and do not clearly distinguish the beneficiaries of "water conservation", that is, the water conservation function, such as the difference in replenishing river runoff and supplying plant growth.

[0005] In comparison, the traditional method can estimate the water conservation capacity more efficiently, making up for the drawback that the isotope method based on estimating the water conservation capacity requires at least one year of data series. However, the advantages of the isotope method are obvious. Therefore, the isotope method is combined with the traditional method to supplement the limitations of the traditional method in revealing the water conservation capacity, and on the other hand, it can be used to compare the differences in estimated water conservation capacity. The water balance method only considers the input and output of water, and estimates the water conservation capacity by subtracting the output water from the input water. The water conservation capacity estimation based on MRT also only considers the input and output of ecosystem water. The joint application of the two methods can avoid the limitations of a single method. Summary of the invention

[0006] In view of this, the present invention provides a method for calculating water conservation capacity.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] A method for calculating water conservation capacity comprises the following steps:

[0009] Step 1: Perform hydrogen and oxygen isotope determination, where the hydrogen and oxygen isotope values ​​are expressed in parts per thousand relative to Vienna standard average ocean water:

[0010]

[0011] Wherein, X represents D or 18 O, D 2 H, δX represents the isotopic composition of hydrogen or oxygen in the sample; Rsample represents the ratio of the abundance of heavy isotopes and light isotopes of hydrogen or oxygen in the extracted water, that is, 18 O / 16 O or D / H; RV-SMOW stands for Vienna Standard Mean Ocean Water (V-SMOW) 18 O / 16 O and D / H values;

[0012] Step 2: Perform wave function simulation and period estimation, in which the average residence time of water in the basin runoff is estimated. The sine function is expressed as:

[0013] δX=C+Asin[ω(day-t)] (2)

[0014] In the formula, δX represents δD or δ 18 O, ‰; C represents the annual average isotope ratio, ‰; A represents the amplitude of the isotope periodic fluctuation, ‰; t represents the phase shift or lag of the curve, rad; ω represents the radial frequency of the periodic fluctuation, rad / d;

[0015] The water retention or transport time in a watershed can be expressed as:

[0016] T=ω -1 [(A s / A r ) -2 -1] 0.5 (3)

[0017] Where As and Ar are the function amplitudes after sinusoidal fitting of runoff water and rainwater isotopes, ‰;

[0018] Step 3: Estimation of oxygen content in water source of the basin, based on the water withdrawal process line: when the surface runoff entering the stream recedes, the stream withdrawal process is controlled by the groundwater discharge process, which can be described as:

[0019] Q t =Q o e -t / τ =Q o k t (4)

[0020] In the formula, Q o , Q t are the runoff flow at time 0 and time t respectively; τ is the turnover period of groundwater storage; k is the water withdrawal constant within a period of time;

[0021] The above formula is based on a linear conservation model, where the groundwater storage S is related to the stream flow Q:

[0022] Q=S / τ=aS (5)

[0023] Where a = 1 / τ;

[0024] Based on average residence time: Based on the calculated average residence time of water in the basin runoff, the water storage in the basin can be expressed as:

[0025]

[0026] In the formula, S o is the annual water storage in the basin, mm; R year is the annual runoff of the basin, mm; MRT is the average residence time of the basin, days.

[0027] Preferably, in step one, the method for collecting field samples for hydrogen and oxygen isotope determination is as follows: a homemade rainfall collection barrel is used for rainfall samples, a funnel is placed at the barrel mouth, and a float is placed in the funnel to prevent water evaporation; runoff samples are directly collected at the basin outlet or target location through a sealed tube; the calculation of water conservation capacity can be completed through seasonal sampling and determination of isotopes of rainfall and runoff samples; when determining the role of water conservation, additional soil or plant samples need to be collected; wherein, soil samples are collected with a soil drill at a layer of 10 cm until the soil drill hits the weathered rock layer, and plant samples are collected with pruning shears or high branch shears Collect one sample from each plant each time from branches that are corky and far away from tillers. When characterizing the changes in the water source of a certain plant, branch samples should be collected from the same main branch, because different main branches correspond to root systems in different positions. The epidermis and cortex of the collected branches should be removed to ensure that there are no green parts on the plant branches. All samples are immediately put into 50ml high-density polyethylene centrifuge tubes after collection, and sealed with parafilm sealing film, placed in ice boxes for refrigeration, and transported back to the laboratory as soon as possible for storage and refrigeration. Liquid samples should be refrigerated at 4℃ and solid samples should be refrigerated at -20℃, and water extraction should be carried out as soon as possible.

[0028] Preferably, in step 1, the indoor processing and analysis method for hydrogen and oxygen isotope determination is: extracting water from soil and plant solid samples using a water vacuum extraction system LI-2000 or LI2100, LICA in the laboratory, filtering the extracted water through a 0.22 μm organic phase needle filter and injecting it into a brown sample bottle, sealing it and refrigerating it at 4°C for determination on the machine; wherein the plant extracted water is measured using a stable isotope ratio mass spectrometer Thermo Scientific MAT 253 connected to an external Flash 2000HT elemental analyzer ElementalAnalyzer, 18 O / 16 The isotope ratios of O and D / H were 1‰ and 0.2‰ respectively; other extracted water samples were analyzed using a stable isotope ratio infrared spectrometer Los Gatos Research 912-0008, 18 O / 16 The isotope ratio accuracies of O and D / H were 0.4‰ and 0.1‰, respectively.

[0029] Preferably, in step 2, the sine equation ω=2π / 365, which is expressed as 2π / 12 if measured in months; in the sine regression analysis, precipitation isotopes use rainfall as weight.

[0030] Preferably, in step three, if the unit is month, the corresponding denominator is 12, wherein formula (4) is applied to the runoff retreat process caused by rainfall, and formula (5) is based on the simulation and estimation results of seasonal changes in runoff isotopes and is applicable to the seasonal scale.

[0031] Compared with the prior art, the present invention has achieved the following technical effects:

[0032] The present invention uses isotope tracing methods to reveal the sources of water in trees and watersheds, and estimates the average residence time of water in the watershed based on seasonal changes, reflecting the length of the water transfer process in the watershed, thereby expanding the understanding of water conservation, from simple estimation of quantity to a common understanding of quantity and function. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The present invention is a general technical flow chart of a method for calculating water conservation capacity. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] A method for calculating water conservation capacity comprises the following steps:

[0036] Said

[0037] In step 1, the method for collecting field samples for hydrogen and oxygen isotope determination is as follows: rainfall samples are collected in a homemade rainfall collection barrel, a funnel is placed at the barrel mouth, and a float is placed in the funnel to prevent water evaporation; runoff samples are directly collected at the basin outlet or target location through a sealed tube; the water conservation capacity can be calculated through seasonal sampling and determination of isotopes of rainfall and runoff samples; when determining the role of water conservation, additional soil or plant samples need to be collected; soil samples are collected with a soil drill at a layer of 10 cm until the soil drill hits the weathered rock layer, and plant samples are collected with pruning shears or high branch shears. One sample was collected from each plant each time; when describing the changes in the water source of a plant, branch samples should be collected from the same main branch, because different main branches correspond to roots in different positions. The epidermis and cortex of the collected branches were removed to ensure that there were no green parts on the plant branches; all samples were immediately put into 50ml high-density polyethylene centrifuge tubes after collection, sealed with parafilm, refrigerated in ice boxes, and transported back to the laboratory as soon as possible for storage and refrigeration. Liquid samples were refrigerated at 4℃ and solid samples were refrigerated at -20℃, and water extraction was carried out as soon as possible.

[0038] The indoor processing and analysis method for hydrogen and oxygen isotope determination is as follows: in the laboratory, the moisture of soil and plant solid samples is extracted using the moisture vacuum extraction system LI-2000 or LI2100, LICA, and the extracted moisture is filtered through a 0.22μm organic phase needle filter and injected into a brown sample bottle, which is then capped and refrigerated at 4°C for determination on the machine; the plant extracted water is measured using a stable isotope ratio mass spectrometer Thermo Scientific MAT 253 connected to an external Flash 2000HT elemental analyzer ElementalAnalyzer. 18 O / 16 The isotope ratios of O and D / H were 1‰ and 0.2‰ respectively; other extracted water samples were analyzed using a stable isotope ratio infrared spectrometer Los Gatos Research 912-0008, 18 O / 16 The isotope ratio accuracies of O and D / H were 0.4‰ and 0.1‰, respectively.

[0039] The hydrogen and oxygen isotope values ​​are expressed in parts per thousand relative to Vienna Standard Average Ocean Water:

[0040]

[0041] Wherein, X represents D or 18 O, D 2 H, δX represents the isotopic composition of hydrogen or oxygen in the sample; Rsample represents the ratio of the abundance of heavy isotopes and light isotopes of hydrogen or oxygen in the extracted water, that is, 18 O / 16 O or D / H; RV-SMOW stands for Vienna Standard Mean Ocean Water (V-SMOW) 18 O / 16 O and D / H values;

[0042] Step 2: Perform wave function simulation and period estimation, in which the average residence time of water in the basin runoff is estimated. The sine function is expressed as:

[0043] δX=C+Asin[ω(day-t)] (2)

[0044] In the formula, δX represents δD or δ 18 O, ‰; C represents the annual average isotope ratio, ‰; A represents the amplitude of the isotope periodic fluctuation, ‰; t represents the phase shift or lag of the curve, rad; ω represents the radial frequency of the periodic fluctuation, rad / d;

[0045] Because rainfall isotopes fluctuate in an annual cycle, the sine equation in this study is ω = 2π / 365, which is expressed as 2π / 12 if it is measured in months. In the sine regression analysis, rainfall isotopes are weighted by rainfall;

[0046] The water retention or transport time in a watershed can be expressed as:

[0047] T=ω -1 [(A s / A r ) -2 -1] 0.5 (3)

[0048] Where As and Ar are the function amplitudes after sinusoidal fitting of runoff water and rainwater isotopes, ‰;

[0049] Step 3: Estimation of oxygen content in water source of the basin, based on the water withdrawal process line: when the surface runoff entering the stream recedes, the stream withdrawal process is controlled by the groundwater discharge process, which can be described as:

[0050] Q t =Q o e -t / τ =Q o k t (4)

[0051] In the formula, Q o , Q t are the runoff flow at time 0 and time t respectively; τ is the turnover period of groundwater storage; k is the water withdrawal constant within a period of time;

[0052] The above formula is based on a linear conservation model, where the groundwater storage S is related to the stream flow Q:

[0053] Q=S / τ=aS (5)

[0054] Where a = 1 / τ;

[0055] Based on average residence time: Based on the calculated average residence time of water in the basin runoff, the water storage in the basin can be expressed as:

[0056]

[0057] In the formula, S o is the annual water storage in the basin, mm; R year is the annual runoff of the basin, mm; MRT is the average residence time of the basin, days.

[0058] If the unit is month, the corresponding denominator is 12. Among them, formula (4) is applied to the runoff retreat process caused by rainfall, and formula (5) is based on the simulation and estimation results of seasonal changes in runoff isotopes and is applicable to the seasonal scale.

[0059] Through the above method, the present invention uses the isotope tracing method to reveal the water sources of trees and watersheds, and estimates the average water retention time of the watershed according to its seasonal changes, reflecting the length of the water transfer process in the watershed, and provides a hydrogen and oxygen isotope tracing technology, thereby expanding the understanding of water conservation, that is, from the simple estimation of quantity to the common understanding of quantity and function, and deeply understanding the technical path of water conservation.

[0060] The above description is only a preferred embodiment of the present invention and does not limit the technical scope of the present invention. Therefore, any slight modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for calculating water conservation capacity, characterized in that: The following steps are involved: Step 1: Perform hydrogen and oxygen isotope determination, where the hydrogen and oxygen isotope values ​​are expressed in parts per thousand relative to Vienna standard average ocean water: Wherein, X represents D or 18 O, D 2 H, δX represents the isotopic composition of hydrogen or oxygen in the sample; Rsample represents the ratio of the abundance of heavy isotopes and light isotopes of hydrogen or oxygen in the extracted water, that is, 18 O / 16 O or D / H; RV-SMOW stands for Vienna Standard Mean Ocean Water (V-SMOW) 18 O / 16 O and D / H values; Step 2: Perform wave function simulation and period estimation, in which the average residence time of water in the basin runoff is estimated. The sine function is expressed as: δX=C+Asin[ω(day-t)] (2) In the formula, δX represents δD or δ 18 O, ‰; C represents the annual average isotope ratio, ‰; A represents the amplitude of the isotope periodic fluctuation, ‰; t represents the phase shift or lag of the curve, rad; ω represents the radial frequency of the periodic fluctuation, rad / d; The water retention or transport time in a watershed can be expressed as: T=ω -1 [(A s / A r ) -2 -1] 0.5 (3) Where As and Ar are the function amplitudes after sinusoidal fitting of runoff water and rainwater isotopes, ‰; Step 3: Estimation of oxygen content in water source of the basin, based on the water withdrawal process line: when the surface runoff entering the stream recedes, the stream withdrawal process is controlled by the groundwater discharge process, which can be described as: Q t =Q o e -t / τ =Q o k t (4) In the formula, Q o , Q t are the runoff flow at time 0 and time t respectively; τ is the turnover period of groundwater storage; k is the water withdrawal constant within a period of time; The above formula is based on a linear conservation model, where the groundwater storage S is related to the stream flow Q: Q=S / τ=aS (5) Where a = 1 / τ; Based on average retention time: Based on the calculated average retention time of water in the basin runoff, the water storage in the basin can be expressed as: In the formula, S o is the annual water storage in the basin, mm; R year is the annual runoff of the basin, mm; MRT is the average residence time of the basin, days.

2. The method for calculating water conservation capacity according to claim 1, characterized in that: In the step 1, the method for collecting field samples for hydrogen and oxygen isotope determination is as follows: a homemade rainfall collection barrel is used for rainfall samples, a funnel is placed at the barrel mouth, and a float is placed in the funnel to prevent water evaporation; runoff samples are directly collected at the basin outlet or target location through a sealed tube; the water conservation amount can be calculated through seasonal isotope sampling and determination of rainfall and runoff samples; when determining the role of water conservation, additional soil or plant samples need to be collected; wherein, soil samples are collected with a soil drill at a layer of 10 cm until the soil drill hits the weathered rock layer, and plant samples are collected with pruning shears or high branch shears One sample is collected from each plant each time from branches that are corked and far away from the tillering. When characterizing the changes in the water source of a certain plant, the branch samples should be collected from the same main branch, because different main branches correspond to root systems in different positions. The epidermis and cortex of the collected branches are removed to ensure that there are no green parts on the plant branches. All samples are immediately put into 50ml high-density polyethylene centrifuge tubes after collection, and sealed with parafilm sealing film, placed in ice boxes for refrigeration, and transported back to the laboratory as soon as possible for storage and refrigeration. Liquid samples are refrigerated at 4℃ and solid samples are refrigerated at -20℃, and water extraction is carried out as soon as possible.

3. The method for calculating water conservation capacity according to claim 1, characterized in that: In step 1, the indoor processing and analysis method for hydrogen and oxygen isotope determination is: in the laboratory, the moisture of soil and plant solid samples is extracted using a moisture vacuum extraction system LI-2000 or LI2100, LICA, and the extracted moisture is filtered through a 0.22 μm organic phase needle filter and injected into a brown sample bottle, which is sealed and refrigerated at 4°C for determination on the machine; wherein the plant extracted water is measured using a stable isotope ratio mass spectrometer ThermoScientific MAT 253 connected to an external Flash 2000HT elemental analyzer ElementalAnalyzer, 18 O / 16 The isotope ratios of O and D / H were 1‰ and 0.2‰ respectively; the other extracted water samples were analyzed by stable isotope ratio infrared spectrometer Los Gatos Research 912-0008, 18 O / 16 The isotope ratio accuracies of O and D / H were 0.4‰ and 0.1‰, respectively.

4. The method for calculating water conservation capacity according to claim 1, characterized in that: In the step 2, the sine equation is ω=2π / 365, which is expressed as 2π / 12 if it is measured in months. In the sine regression analysis, the precipitation isotope uses rainfall as the weight.

5. The method for calculating water conservation capacity according to claim 1, characterized in that: In step 3, if the unit is month, the corresponding denominator is 12, wherein formula (4) is applied to the runoff retreat process caused by rainfall, and formula (5) is based on the simulation and estimation results of seasonal changes in runoff isotopes and is applicable to the seasonal scale.

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