The Heinz Center's State of the Nation's Ecosystems
ecosystem: Grasslands and Shrublands
indicator Name: Number and Duration of Dry Periods in Grassland/Shrubland Streams and Rivers: Duration of Zero-Flow Periods
page # in printed report: 166
location on page: lower
data source: U.S. Geological Survey; analysis by the University of Colorado. Coverage: grassland/shrubland regions (see map in Grasslands and Shrublands Introduction) in lower 48 states.
notes: please see technical notes for further details on accessing these data from their original source; this data table comes from a specific graphic in The State of the Nation's Ecosystems report (www.heinzctr.org/ecosystems)

units: % of all sites with zero flow
  1950s 1960s 1970s 1980s 1990s
Substantially Longer 37.57 20.63 4.76 4.76 9.52
Substantially Shorter 23.28 30.69 60.32 64.02 62.96