Threat Assessments on California Rangelands

Water-Wildlife Hotspots

Example hotspot Map

These maps display percent change in water availability relative to the 1981-2010 climate period where 5% or more of watershed area has lost critical habitat. Water-wildlife hotspots are those areas where changes in water availability (recharge plus runoff) and loss of critical habitat coincide. Water availability is defined as recharge plus runoff. Critical habitat is defined as critical priority conservation areas mapped in the California Rangeland Conservation Coalition's focus area map ( (TNC, 2007). Percent change in water availability is provided for two climate projections for each of the three IPCC-SRES scenarios – A1B, A2 and B1. Scenarios of critical habitat loss for years 2040, 2070 and 2100 were coupled with percent change in water availability for climate periods 2010-2039, 2040-2069 and 2070-2099, respectively. In some scenarios and time periods, no water-wildlife hotspots exist. Watershed boundaries are from the 8-digit Watershed Boundary Dataset (

Loss of critical habitat was identified in this project's critical habitat change maps. Future change in water availability was modeled using the U.S. Geological Survey's Basin Characterization Model (BCM), a regional water balance model (Flint et al. 2013, Flint and Flint, 2012). The BCM was run with two statistically downscaled global climate models (GCMs) (a warm, wet future and a hot, dry future) for each emissions scenario (see Recharge/Runoff description page for model details). Important hotspots are those watersheds where water availability is greatly reduced (labeled in dark red), though areas where water availability becomes more plentiful are also identified (labeled in blue).

Thirty-year water year summaries of the sum of recharge and runoff were used for this rangelands project. The maps display percent change in the sum of 30-year averages of recharge to runoff, averaged by watershed area. Percent change in water availability is calculated as:

ΔW = [(Wx – W1981-2010)/ W1981-2010]*100
Wx = Rchx + Runx


  • ΔW = percent change in water availability
  • Wx = average water availability for climate period x
  • W1981-2010 = average water availability for climate period 1981-2010
  • Rchx = average recharge for climate period x, averaged by watershed area
  • Runx = average runoff for climate period x, averaged by watershed area


Flint, L.E., A.L. Flint, J.H. Thorne, and R. Boynton. 2013. Fine-scale hydrologic modeling for regional landscape applications: the California Basin Characterization Model development and performance. Ecological Processes 2:25. Available online at:

Flint, L.E. and Flint A.L. 2012. Downscaling future climate scenarios to fine scales for hydrologic and ecologic modeling and analysis. Ecological Processes 1:2. Available online at:

The Nature Conservancy (TNC). 2007. California Rangeland Conservation Coalition Biological Prioritization of Rangelands: Approach and Methods. Available online at: