Arizona Rivers & Water

Water is fundamental to life for people, plants, and animals. We have studied and mapped perennial waters, native fish distributions, and threatened & endangered riparian species throughout Arizona. We have also identified the groundwater aquifers that sustain perennial rivers and streams such as the San Pedro and Verde Rivers.

Water — a rare resource in the Southwest

Rivers, streams, and wetlands are critically important to animals and plants in the arid Southwest, and are key to supporting vibrant human economies with a high quality of life. Growing human populations have increased the demand for water, sometimes at the expense of stream-dependent species.

Understanding this confluence of water demands rests at the core of any efforts to make human communities sustainable on the Arizona landscape and to keep our precious heritage alive.

Arizona Freshwater Assessment

We have integrated three statewide data sets and regional stream monitoring data into a single data package, the Arizona Freshwater Assessment. The assessment includes:

• the historical and current extent of surface flow for our state’s rivers and streams,
• habitat maps of Arizona’s 33 native fish species,
• the distribution of all threatened and endangered aquatic and riparian species

Historical and current status of perennial river flow

Key to managing our water, wildlife, and riparian areas is understanding which portions of our streams flow perennially and are supported by groundwater, and which portions only flow intermittently due to storm runoff events. To facilitate better planning, analysis, and sustainable water management, we developed a GIS data set using 3 primary data sources:

• A map published in 1981 by the Arizona Game & Fish Department showing formerly perennial stream reaches which we digitized,
• Data on current perennial flow from the Arizona Department of Water Resources
• Data depicting the portions of our rivers that are regulated by dams and diversions.

Comparing the current and historical data illustrates the changes to Arizona’s rivers: Arizona has lost 35% of our natural perennial flow. The loss has been greatest on Arizona’s big rivers – the Colorado, Gila, Salt, and Verde rivers – where 91% of free-flowing perennial miles have been lost.

Habitat maps of Arizona’s 33 native fish species

We modeled and mapped the recent distribution of 33 native fish species throughout Arizona. Individual species distributions or a composite of all 33 species distributions illustrate patterns of species richness and potential habitat. We published a companion report, Habitat Mapping and Conservation Analysis to Identify Critical Streams for Arizona’s Native Fish, in the journal Aquatic Conservation: Marine and Freshwater Ecosystems.

Distribution of threatened and endangered aquatic and riparian species

We created a stream-level attribution for the presence of riparian and aquatic species with threatened or endangered status under the Endangered Species Act. This can be used to quickly identify the rivers and streams that are important for our federally protected species.

Wet-dry mapping for southern Arizona streams

The Nature Conservancy, together with public and private collaborators & volunteers, have conducted annual monitoring of several rivers and streams in southern Arizona to map the extent of perennial surface flow during the driest time of the summer. These data provide annual snapshots of each river’s status and enable multi-year comparisons.

We presently have compiled the results of surveys on the San Pedro River, and will add data for Cienega Creek and Sonoita Creek in the future.