Iowa Precipitation Monitoring for the National Trends Network

PERIOD OF PROJECT: Continuous since 1984
PROJECT CHIEF: S. Mike Linhart Email S. Mike Linhart
STUDY AREA: Clayton and Lucas Counties
COOPERATING AGENCIES: US Geological Survey (Federal program)


The amount of substances dispersed into the atmosphere and deposited by precipitation, aerosols, and gases is expected to continue to increase throughout North America. Thus, there is an increasing need for careful, coordinated measurement on a National scale of the amounts, nature, and effects of these substances. To establish long-term trends in composition and flux, it is necessary that these measurements be made for a period of at least 10 years. These measurements will be used to assess the link between environmental effects and atmospheric deposition and will provide the information necessary for the responsible management of agricultural, forest, and aquatic ecosystems of the United States.


The Iowa precipitation-monitoring stations are part of the National Atmospheric Deposition Program/National Trends Network (NADP/NTN) program which provides a regional-to-national overview of chemical composition of atmospheric deposition in the United States. This program includes scientific research in atmospheric deposition, monitoring, and assessment activities. Information from this overview is being used to discover and characterize environmentally important geographical and temporal trends in the chemical climate of North America. In addition, information from this national program is being used to assess the effects of atmospheric deposition on:

  1. The productivity of Agricultural and Forest Lands.
  2. The health of Domestic Animals, Wildlife, and Fish.
  3. The chemistry of Surface and Groundwater.
  4. Visibility and Materials.


Wet deposition samples are collected weekly at the two Iowa National Trends Network sites. One is at Big Springs Fish Hatchery in Clayton County (425435091281101), and the other is at the McNay Research Station in Lucas County (405747093233201). Field values of pH and specific conductance and the chemical analyses of the precipitation are published in the Annual Data Report, as well as in the National Atmospheric Deposition Program/National Trends Network Annual Data Summary of Precipitation Chemistry in the United States. Beginning in 2005, collection of field pH and specific conductance were discontinued. This decision by the NADP/NTN program office was based on several factors which include; comparisons showing small differences between field and laboratory pH values (since 1994), reduction of sample handling by site operators to minimize the possibility of contamination, increasing the volume of precipitation available for laboratory chemistry analysis, and to allocate freed resources for network improvements (NADP Data Report 2004-02: Discontinuation of Support for Field Chemistry Measurements in the National Atmospheric Deposition Program National Trends Network (NADP/NTN). Annual data reports from water years 1998 through 2010 are currently on-line under Publications, and the 2011 water year data should be on-line in 2012.