Calculation method for underground water critical depth on condition of phreatic evaporation
Calculation method for underground water critical depth on condition of phreatic evaporation
 CN 105,005,687 A
 Filed: 07/02/2015
 Published: 10/28/2015
 Est. Priority Date: 07/02/2015
 Status: Active Grant
First Claim
1. the computing method of critical depth of groundwater under an evaporation from phreatic water condition, it is characterized in that:
 these computing method, based on the computing method of the one dimension homogeneous soil steady state evaporation model of MualemVan Genuchten characteristic curve of soil moisture equation and Gardner, comprise the following steps;
Step 1, the area determining survey region and calculation interval;
Step 2, determine the parameter of the MualemVan Genuchten characteristic curve of soil moisture equation of survey region;
With the MualemVan Genuchten characteristic curve of soil moisture equation of parameter l such as formula (1) and (2),K(h)＝
K _{s}Θ
^{l}[1(1Θ
^{1/m}) ^{m}] ^{2}. (1)
Chinese PRB Reexamination
Abstract
A calculation method for underground water critical depth on a condition of phreatic evaporation belongs to a calculation method for underground water critical depth. The calculation method is on the basis of MualemVan Genuchten soil moisture characteristic curve equation and a onedimensional homogeneous soil steady state evaporation model of Gardner. The calculation method comprises the following steps of: 1, determining the area of a study region and a calculation time interval; 2, determining parameters of the MualemVan Genuchten soil moisture characteristic curve equation of the study region; 3, determining calculation surface soil evaporation intensity of the study region and a soil negative pressure absolute value of an earth surface; and 4, calculating the underground water critical depth of the study region on the condition of phreatic evaporation. The calculation method for the underground water critical depth has the advantages that the underground water critical depth can be rapidly and effectively calculated, the calculation result is contributed to a favorable reference value and beneficial for engineering research staff to use, the technical problems of the blank in the calculation method for the underground water critical depth and value uncertainty are solved, and the calculation method can be applicable for different places and different soil types.

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5 Claims

1. the computing method of critical depth of groundwater under an evaporation from phreatic water condition, it is characterized in that:
 these computing method, based on the computing method of the one dimension homogeneous soil steady state evaporation model of MualemVan Genuchten characteristic curve of soil moisture equation and Gardner, comprise the following steps;
Step 1, the area determining survey region and calculation interval; Step 2, determine the parameter of the MualemVan Genuchten characteristic curve of soil moisture equation of survey region; With the MualemVan Genuchten characteristic curve of soil moisture equation of parameter l such as formula (1) and (2), K(h)＝
K _{s}Θ
^{l}[1(1Θ
^{1/m}) ^{m}] ^{2}. (1)
 these computing method, based on the computing method of the one dimension homogeneous soil steady state evaporation model of MualemVan Genuchten characteristic curve of soil moisture equation and Gardner, comprise the following steps;

2. the computing method of critical depth of groundwater under a kind of evaporation from phreatic water condition according to claim 1, it is characterized in that:
 in step 1, the area of described survey region is greater than 10000m ^{2}, soil characteristic, hydrogeological condition, underground water situation and people all have difference for measure, carry out subregion research, and final critical depth of groundwater is determined with the area weighted average of each district calculated value;
Described calculation interval refers to, and will to study critical depth be average annual critical depth or certain month critical depth;
When being average annual critical depth, then evaporation capacity E _{y}should be the daily mean of the average annual evaporation capacity of (35) year meteorological data;
When being certain month critical depth, then evaporation capacity E _{m}should be the daily mean of certain monthly evaporation capacity of (35) year meteorological data.
 in step 1, the area of described survey region is greater than 10000m ^{2}, soil characteristic, hydrogeological condition, underground water situation and people all have difference for measure, carry out subregion research, and final critical depth of groundwater is determined with the area weighted average of each district calculated value;

3. the computing method of critical depth of groundwater under a kind of evaporation from phreatic water condition according to claim 1, is characterized in that:
 in step 2, described parameter (θ
_{s}, θ
_{r}, α
, K _{s}, n, m and determination l) adopt site test method, Lab Test Method, soil restructuring method and literature survey method;
The priority ranking of four kinds of methods is followed successively by site test method, Lab Test Method, soil restructuring method, literature survey method;
Described site test method, adopts horizontal soil column method to determine K _{s};
Adopt onsite soil suction head and volumetric water content measured value, by least square method or RETC software nucleoid θ
_{s}, θ
_{r}, α
, n, m and l;
Described Lab Test Method, uses characteristic curve of soil moisture analyzer, determines θ
_{s}, θ
_{r}, α
, K _{s}, n, m and l;
Described soil restructuring method, according to onsite soil basic physical parameters, by the soil restructuring of locality existing on document, determines θ
_{s}, θ
_{r}, α
, K _{s}, n, m and l;
Described literature survey method, by the parameter of characteristic curve of soil moisture equation existing on document, determines θ
_{s}, θ
_{r}, α
, K _{s}, n, m and l.
 in step 2, described parameter (θ

4. the computing method of critical depth of groundwater under a kind of evaporation from phreatic water condition according to claim 1, is characterized in that:
 in step 3, and described reckoner soil evaporation capacity is 0.1E _{y}or E _{m};
When there being field test data, obtain the soil negative pressure absolute value at earth'"'"'s surface place;
When not having field test data, the soil negative pressure absolute value at earth'"'"'s surface place can get 15000cm.
 in step 3, and described reckoner soil evaporation capacity is 0.1E _{y}or E _{m};

5. the computing method of critical depth of groundwater under a kind of evaporation from phreatic water condition according to claim 1, it is characterized in that:
 in step 4, realized by simultaneous formula (1), (2) and (3), or realize based on Matlab or Fortran language compilation;
Soil negative pressure absolute value is in 01cm constant interval, and △
h is less than or equal to 0.1cm;
Soil negative pressure absolute value is in 1100cm constant interval, and △
h is less than or equal to 1cm;
Soil negative pressure absolute value is being greater than in 100 constant intervals, and △
h is more than or equal to 1cm, is not more than 10cm.
 in step 4, realized by simultaneous formula (1), (2) and (3), or realize based on Matlab or Fortran language compilation;
Specification(s)