This is a first in a series of posts that chronicle our experiences discovering, compiling, and making groundwater data understandable in California.
A myriad of agencies at the local, state, and federal level collect data on groundwater quality and quantity. As expected, data formats vary and methods for retrieving data vary similarly. One agency often leads to another, and there is a high volume of what appear to be redundant data sets. (we will verify redundancy where we find it and update this post).
The canvas that we will be overlaying our data both historical and instantaneous will be on a color coded map of aquifer boundaries. Aquifers are geologic material that transmit water underground. Aquifers allow for water to move, while “aquitards” have low permeability and slow or stop the movement of water.
a primer on aquifer basics (colors to do not correspond to maps shown below)
(image courtesy of the USGS's "Aquifer Basics", 2013)
The USGS has a national map of “Principal Aquifers” made up of six rock types, and boundaries for “Aquifers of Alluvial and Glacial Origin” contained in a separate file. White lines are county borders and black lines are aquifer boudaries.
Aquifers of Alluvial and Glacial Origin (shown in green)
Files are provided as *.shp files here:
Principal Aquifers (2002)
Aquifers of Alluvial and Glacial Origin (2003)
Tables offer the six corresponding aquifer types where ROCK_TYPE 999 is an aquitard:
ROCK_TYPE | ROCK_NAME
100 | Unconsolidated sand and gravel aquifers
200 | Semiconsolidated sand aquifers
300 | Sandstone aquifers
400 | Carbonate-rock aquifers
500 | Sandstone and carbonate-rock aquifers
600 | Igneous and metamorphic-rock aquifers
999 | NULL
A corser map of aquifers specific to California can be found through the California Department of Water Resources:
Bulletin 118 Basin Boundaries (2010)
The table values reveal a subdivision of major aquifers into sub-basins and include a water budget (BUDGET_TYP) for each sub-basin.
(image courtesy of the DWR's "Bulletin 118", 2010)
In our next installment, we will investigate water quantity point data for both historical and instantaneous data amassed by a distributed system of remote sensors.