CREP: 10 years of rebuilding Iowa wetlands
The Iowa Conservation Reserve Enhancement Program, or CREP, celebrates its 10th anniversary in 2011. At the 2001 Iowa State Fair, the Iowa CREP agreement was signed, which created the water quality program.
Ten years later, CREP continues to develop cutting-edge technology for watershed-scale nutrient reductions that can be obtained by targeting wetland restorations to the sweet spots on the landscape that provide the greatest water quality benefits.
What is CREP? This program is a joint effort of the Iowa Department of Agriculture and Land Stewardship, or IDALS, and the USDA Farm Service Agency, in cooperation with local soil and water conservation districts. The program provides incentives to landowners to voluntarily restore wetlands targeted for water quality improvement in the heavily tile-drained regions of Iowa.
Enrollment is on a continuous basis in 37 eligible counties in north-central Iowa. The goal of the program is to reduce nitrogen loads and movement of other ag chemicals from croplands to streams and rivers. CREP wetlands are designed to receive tile drainage by gravity flow, treating the water before it enters streams and rivers.
Excess nitrogen not only affects Iowa’s waters, but also is one of the leading causes of hypoxia in the Gulf of Mexico. Hypoxia (low oxygen) reduces the productivity of the Gulf, leading to the commonly referred to “dead zone.” CREP wetlands are one strategy to help reduce nitrogen loading to these waters.
Targeting is the key
To ensure these wetlands are established so that they are targeted to the most advantageous locations, IDALS uses advanced geographic information system analyses to find locations that are properly sized and situated to provide large nitrogen-removal benefits. Wetland sizing criteria are based on several years of research conducted by Iowa State University.
• Drainage area feeding to the wetland must be between 500 and 4,000 acres.
• Wetland pool area must be between 0.5% and 2% of its watershed area (i.e., a 1,000-acre watershed would require a wetland between 5 and 20 acres in size).
• The buffer-to-wetland pool ratio shouldn’t exceed 4 to 1.
• Deep-water area (greater than 3 feet deep) of the wetland is not to exceed 25% of the total wetland area.
• All tile drainage outlets entering the wetland must have at least 1 foot of separation above the design water level of the wetland to protect drainage rights.
Incentives to enroll
Landowners enrolling in CREP receive 100% cost-share for the wetland restoration. In addition to the cost-share on restoration, the landowners receive 15 years of annual Conservation Reserve Program payments from FSA valued at 150% of the average soil rental rate of the land enrolled.
IDALS also pays a market-based easement payment with the options being either a 30-year or permanent easement. The easement payments are indexed to the full agricultural value of the land as reported annually by ISU. Easements remain private property because landowners maintain ownership and, therefore, control access to the area.
How do these restored wetlands work? Research and monitoring by ISU has demonstrated that strategically sited and designed CREP wetlands remove 40% to 70% of nitrates and more than 90% of herbicides from cropland drainage waters.
Nitrogen reduction is primarily achieved thanks to the naturally occurring denitrifying bacteria in wetlands. Through denitrification, the bacteria remove nitrate from the water and release it as nitrogen gas into the air as an innocuous end product. It is commonly cited that 78% of the air we breathe is nitrogen gas.
10 years of progress
The highly targeted nature of this program has led to 72 wetlands currently restored or under development over the past 10 years that will provide water quality benefits to 86,000 acres of land by removing more than 54,000 tons of nitrates during their lifetime.
These 72 targeted restorations total more than 700 acres of wetland, plus more than 2,500 acres of surrounding buffers that are planted to native prairie vegetation. Even with the positive results so far, CREP continues to explore the latest technology to optimize wetland performance while incorporating additional considerations for habitat and temporary floodwater storage benefits.
Asberry is a program planner with the Division of Soil Conservation at IDALS in Des Moines. Email her at Sarah.Asberry@iowaagriculture.gov.
NATURE’S FILTER: A wetland works to filter out nitrates and other agricultural chemicals from groundwater. CREP is a program that restores these naturally occurring wetlands on tile-drained landscapes. This Dallas County CREP wetland was on the Iowa Learning Farms tour.
This article published in the August, 2011 edition of WALLACES FARMER.
All rights reserved. Copyright Farm Progress Cos. 2011.