Experiments with Yolo County Groundwater Data

Submitted by dylan on Tue, 2005-08-09 18:08.
Yolo Groundwater Map 1

Figure 1

The California Department of Water Resources provides public access to their groundwater level and quality databases here. Point data (well locations) associated with groundwater levels can be downloaded in the form of a text file, which can then be input into the GIS/mapping application of choice. Simple UNIX text programs were used to extract geographic coordinates and groundwater level, and imported into GRASS GIS with the command v.in.ascii. Pre-computer groundwater contours can also me downloaded from the Water Resources webpage.

 
An example procedure for processing groundwater records from the Department of Water Resources with open source tools is listed below:

# 1. re-project source DEM data to UTM z10
gdalwarp -t_srs '+proj=utm +zone=10 +datum=NAD83' \
-s_srs '+proj=aea +x_0=0.0 +y_0=-4000000 +lon_0=-120.0 +lat_0=0.0 +lat_1=34.0 +lat_2=40.5 \
+datum=NAD83' 38121/hdr.adf elev.tif

# 2. import dem into GRASS with r.in.gdal

# 3. input Dept. Water Resources data into GRASS
v.in.ascii in=wells.txt out=wells2 columns='x double precision, y double precision, GSWS double precision'

# 4. interpolate surface with RST
v.surf.rst in=wells2 zcol=GSWS elev=gsws

Figure 1 illustrates an example of an interpolated groundwater surface in Yolo County. Interpolation was done in GRASS-6.1, using the RST (regularized splines with tension) method (see references 1 and 2). Figures 2 and 3 are examples of 3D visualization of groundwater surface, groundwater contours, and local elevation data with the GRASS add-on, NVIZ. Other grographic data used in this example (30 DEM and Yolo County outline) were downloaded from ca.gis.gov. The DEM data was re-projected from the Teal Albers coordinate system to UTM zone 10 with the open source tool gdalwarp (part of the GDAL/OGR geospatial data processing tools available here). Note that the 30 meter elevation products distributed on gis.ca.gov are in the ARC/INFO binary grid format.

Yolo County Groundwater 3D View 1

Figure 2
Yolo County Groundwater 3D View 2

Figure 3

 
References
1. Mitasova and Mitas 1993: Interpolation by Regularized Spline with Tension: I. Theory and Implementation, Mathematical Geology ,25, 641-655.
2. Mitasova and Hofierka 1993: Interpolation by Regularized Spline with Tension: II. Application to Terrain Modeling and Surface Geometry Analysis, Mathematical Geology 25, 657-667.

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