CRDSS_Task1_14-17_SoilCharacteristics

• Title: CRDSS Task 1.14-17 - Consumptive Use Model - Soil Characteristics for the Consumptive Use Model
• Description: This document describes the methodology used to convert spatial soil texture data to an available water holding capacity and soil surface texture.
• Decision Support - Doc Type: Task Memorandum
• Date: 1/9/1995
• DSS Category: Consumptive Use
• DSS: Colorado River
• Basin: Colorado Mainstem
• Contract/PO #: C153658, C153727, C153752
• Grant Type: Non-Reimbursable
• Bill Number: SB92-87, HB93-1273, SB94-029, HB95-1155, SB96-153, HB97-008
• Prepared By: Riverside Technology inc.

sand3 3 I
silt3 3 I
clay3 3 I
texttot3 3 N 3
.
4.Relate to comp by the item Run the program CALCSSC.AML to generate
soilw.pat muid
( ).
a sand, silt and clay percentage for each mapping unit This program multiplies the
muid
'
sand, silt, and clay percentages for each by the s component percentage
seqnum seqnum
( ) and then sums the sand, silt, and clay percentages for each individual mapping unit
comppct
( ). When with a texture of bedrock (i.e. sand, silt, and clay are 0) occur, the total
muid sequa
sand, silt, and clay for each mapping unit will be less than 100. In these cases the sand, silt, and
clay percentages were pro-rated based on 100 percent and adjusted accordingly. When the final
sand, silt, and clay textures for the mapping units were summed, it was found that some
mapping units had a textural total of 99.999 or 100.001 because of the bedrock adjustment. In
these cases, .001 was either added to or subtracted from the sand percentage to reach the value
of 100 percent (sand + silt + clay).
5.Use the percent of sand, silt, and clay to determine the textural class for each mapping unit
( ).
Using the sand, silt, and clay percentages (for each mapping unit), the textural class
muid
was determined using the Soil triangle of the basic soil textural classes as presented in the
Drainage Manual (USBR 1993). A FORTRAN program was written ( ) to
surftext.f
determine the soil class based on a tabular representation of the Soil triangle. The tabular
representation of the Soil triangle as presented in the Drainage Manual (USBR 1993) allows for
some overlap between a few textural classes. The few mapping units that showed two soil
textures were corrected by hand.
3.0 CONCLUSIONS AND RECOMMENDATIONS
Available water capacity and surface texture values were developed from STATSGO data for the
consumptive use (CU) model. The result is a set of GIS coverages that can be used to estimated
consumptive use for irrigated agricultural land.
4
A275 01.09.95 1.14-17 CSU IDS