Shared data + powerful technology = informed water management

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shows classified areas of residential and commercial land as well as the CAP canal

What happens when CAP analysts combine freely available GIS data with powerful technology? They find themselves knee deep in a project with a goal to more accurately identify types of outdoor water uses – critical information for water planning at CAP and for the municipal water providers within CAP’s three-county service area.

In the simplest of terms, CAP’s Resource Planning and Analysis Department and Analytics and Information Management (AIM) Department take data from different sources to determine how land is used in Maricopa, Pinal and Pima counties, (CAP’s service area) – specifically how much of the land requires watering.

The project is anything but simple. These analysts start with aerial imagery and data from the U.S. Department of Agriculture’s National Agriculture Imagery Program, or NAIP. This aerial imagery is gathered during the agricultural growing season and can be used to calculate a normalized difference vegetation index (NDVI), which is able to distinguish water, vegetation, non-vegetation, and artificial turf. Great data, but it doesn’t distinguish between a bush, grass, cactus, or tree, which makes a difference when you are trying to determine water use.

ClassificationV2- the picture shows how raw NAIP imagery looks for an area compared to the classified version. The result is GIS data that distinguishes between land use types.

So next, they utilize light detection and ranging data, also known as LiDAR, from the U.S. Geological Service’s 3D Elevation Program (3DEP). This remote sensing method generates an accurate, three-dimensional rendering of the area. This additional information allows for a more detailed breakdown of vegetation by height, making it possible for water planners and managers to separate trees from groundcover and potential grass.

LiDAR- the picture shows an illustration of how 3D LiDAR data captures the shape of objects above ground.

They have encountered some challenges in the process, such as unhealthy grass, shadows and artificial turf. But they are overcoming those challenges and moving forward to uncover trends, improve supply and demand models, and support planning work across the CAP service area. CAP is also exploring opportunities to share these data for planning purposes, so water managers and researchers have as much information as possible to effectively manage their water supplies.