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Walnut Gulch Experimental Watershed, Arizona (Runoff)

posted on 2024-02-13, 14:01 authored by Dave Goodrich

The Walnut Gulch Experimental Watershed (WGEW) runoff database has the longest period of record of runoff in the world for a semiarid location, with data collection beginning in 1953. Runoff occurs at Walnut Gulch primarily as a result of convective thunderstorms during the months of July through September. Runoff volume and flow duration are correlated with drainage area as a result of the limited areal extent of runoff producing rainfall and transmission losses or infiltration of the flood wave into the channel alluvium. Runoff is measured at three ranges of watershed size: small, 0.0018-0.059 km2; medium, 0.35-1.60 km2; and large, 2.27-149 km2. The small watersheds are termed ‘‘unit source area watersheds'' and were established to quantify the interaction of rainfall intensity patterns, soils, vegetation, and management on the rates and amounts runoff and sediment production. The medium watersheds were established at preexisting small earthen dams or stock tanks to obtain inexpensive measurements of storm runoff volume and annual sediment yield. The large watersheds were established to quantify the effects of the spatial and temporal variability of thunderstorm rainfall and channel characteristics on water yield, peak discharge, and sediment yield. Runoff was originally measured using a stilling well, float, and analog stage recorders (Stevens A-35, Friez FD-4, Friez FW-1) with mechanical clocks to record the timing of the event. In 1999, digital recorders consisting of potentiometers attached to the stilling well gear mechanism and a Campbell Scientific CR-10 data logger were added to all of the runoff measurement stations. At present, both the analog and digital data are being collected and are archived.

Resources in this dataset:




Data contact name

Armendariz, Gerardo


USDA Agricultural Research Service

Intended use

The runoff data have been the basis for semiarid region flood frequency analysis and, in conjunction with rainfall data from the intensive recording rain gauge network, are the basis for understanding rainfall-runoff processes at a range of scales and watershed-scale model development, testing, and validation. Early research focused on describing hydrograph characteristics and the relationship between rainfall and runoff at a range of scales.

Use limitations

The measurement of runoff at Walnut Gulch is affected by the ephemeral nature of the runoff, high flow velocities, high sediment concentrations in the flow, and the initial upstream channel geometry created by the previous flow(s) sediment transport/deposition. The high sediment loads present a problem for structures that measure runoff stage at critical depth. Structures such as weirs and zero slope flumes retard the flow velocity to tranquil or subcritical conditions that, for sediment-laden flows, cause sediment deposition in the pond above or within the measurement section and invalidate the stage-discharge relationship of the measurement structure. Because of this, runoff measurement at Walnut Gulch has relied on supercritical flumes that channel the flow through the structure at a velocity high enough to minimize sediment deposition within the measurement section.

Temporal Extent Start Date



  • Not specified

Geographic Coverage


ISO Topic Category

  • environment
  • farming

Ag Data Commons Group

  • Walnut Gulch Experimental Watershed
  • Long-Term Agroecosystem Research

National Agricultural Library Thesaurus terms

watersheds; data collection; storms; drainage; rain; alluvium; rain intensity; soil; vegetation; tanks; stormwater; sediment yield; temporal variation; potentiometers; microprocessors; digital database; semiarid zones; meteorological data; rain gauges; runoff; models; hydrograph

OMB Bureau Code

  • 005:18 - Agricultural Research Service

OMB Program Code

  • 005:040 - National Research

ARS National Program Number

  • 211

Pending citation

  • No

Public Access Level

  • Public

Preferred dataset citation

Goodrich, Dave (2020). Walnut Gulch Experimental Watershed, Arizona (Runoff). USDA Agricultural Research Service.