Revised Universal Soil Loss Equation 1.06 - Current Version

Current Version

Version 1.06c is the current (February 20, 2004) version of RUSLE1.06 being released by the USDA-Agricultural Research Service (ARS) for general use. It, along with data files, can be downloaded from this Internet site.

RUSLE1.06c is land use independent and applies to all land uses where mineral soil is exposed to the erosive forces of raindrop impact and overland flow. RUSLE1.06c applies to all land uses including cropland. RUSLE1.06c is not specific to construction sites

Significant changes were incorporated in RUSLE1.06c so that it gives soil loss estimates that are comparable with those estimated by the recently released RUSLE2. If you have been using previous versions of RUSLE1.06, you should upgrade to RUSLE1.06c. Changes between RUSLE1.06b and RUSLE1.06c include:

1. New erosivity R-values based on modern climate data have been developed for RUSLE2. These new values should be used in RUSLE1.06c. The RUSLE1.06c citylist database that is downloaded from this site when RUSLE1.06c is downloaded contains the new R-values. Overall, erosivity based on modern climate data is about 10% higher than based on the climate data previously used in the USLE and RUSLE1. See the Bulletin section for additional information, including an erosivity map for the eastern US.

2. A new map for 10 -Yr EI values was developed for use in RUSLE1.06c. New values from this map have been included in the RUSLE1.06c database that is downloaded when RUSLE1.06c is downloaded from this Internet. See the Bulletin section for additional information, including the new map of 10 -Yr EI values for the eastern US.

3. Equation 5-9 in Agriculture Handbook (AH) 703, which was incorrectly programmed in previous versions of RUSLE1.06, has been corrected in RUSLE1.06c. Correction of this error has little effect except for high amounts of soil biomass.

4. An interaction between canopy and ground cover was added to RUSLE1.06c. This interaction is the same as the one described in AH537 for the USLE. RUSLE1.06c computes increased soil loss for high canopy covers close to the ground. Using a 100% canopy cover close to the ground can not be used in RUSLE1.06c to effectively "shut off" soil loss for conditions like a flooded rice field or plastic-covered soil.

5. RUSLE1.06c computes less reduction in soil loss for no-till cropping systems, especially for high ground cover values, than do previous versions of RUSLE1.06. Soil loss values computed by previous versions of RUSLE1.06 were judged to be too high for no-till cropping systems.

6. RUSLE1.06c does not use a temporal variation in the soil erodibility factor. This change can affect soil loss values by about 25% in certain locations including the Midwestern and Northeastern regions of the US.

7. A change in the cursor operation was made for the time invariant C factor to clarify selection of the b value for the ground cover effect. This change has no effect on computed soil loss.

8. An error was fixed that prevented saving an Req climate file where an Req value had been manually entered.

9. The Req El distribution for Req areas was changed from a 95-5 distribution of soil loss from the winter period to the summer period to an 87-13 distribution. The new distribution was based on recent analysis of erosion data.

RUSLE1 was first released for widespread use in late 1992 as version 1.02. Improved versions of RUSLE were periodically released to correct errors and to give RUSLE increased capability. Previous versions of RUSLE were available for fee from the Soil and Water Conservation Society (SWCS) through a Cooperative Research and Development Agreement with ARS that gave the SWCS a copyright on RUSLE1. That agreement expired in 1996. The last version of RUSLE1 covered by that agreement was RUSLE1.05. Version 1.06c is not covered by the copyright and can be freely downloaded and used without payment of a fee.

Version 1.04 was the last version of RUSLE1 distributed by the SWCS. Version 1.05 was released to the SWCS but was never sold to the public. Version 1.06c supersedes all previous versions of RUSLE1. Should you need a copy of version 1.02, 1.03, or 1.04 contact the SWCS. Should you need a copy of RUSLE1.05, contact Dave Lightle of the USDA-Natural Resources Conservation Service (NRCS) dave.lightle@lin.usda.gov.

Version 1.04 included major improvements in the C factor for rangelands and no-till cropland. RUSLE1.05 improved the handling of residue for crops that senesced, the computation of the effects of mechanical disturbance on rangelands, and the effect of row grade on soil loss in low rainfall areas.

New features in version 1.06 included computation of deposition on concave slopes, in terrace channels, and in sediment basins as a function of sediment characteristics; computation of deposition in terrace channels as a function of the incoming sediment load and the transport capacity in the terrace channel; computation of b values for the effectiveness of ground cover based on land use, slope steepness, and the ratio of rill to interrill erodibility; computation of the slope length factor from an estimate of the ratio of rill to interrill erosion, slope steepness, and land use; and improved computation of the effectiveness of ground cover on steep slopes at construction sites. RUSLE1.06b version also contains a calculation change for the soil moisture (SM) subfactor of the cover-management (C) factor.

The USDA (NRCS) implemented RUSLE1.05 in its field offices. Implementation of RUSLE1.04 was underway by the USDA-NRCS when a problem was discovered in the way that RUSLE1.04 handled residue for crops like soybeans that senesce and drop leaves to the soil surface. That problem was corrected in an interim version of RUSLE, known as version 1.05d.

Most of NRCS implemented version 1.05d, although the southern and eastern states implemented 1.04, but adjusted parameter values in databases to minimize the senescence problem. In most states, NRCS released RUSLE1.05 in the form of hardcopy tables and figures placed in their Field Office Technical Guides.

Another interim version, 1.05q, was adopted by NRCS in 1997 for use in its Field Office Computing Systems (FOCS) software. This UNIX-based model was implemented in field offices in several states. The differences between this version and 1.05d were in computations for stripcropping and the time invariant C and P factors for rangelands. The "official" (publicly released) version of RUSLE1.05 was released in September 1996.

NRCS is now implementing RUSLE2 in its field offices as a replacement for RUSLE1.05.