What in the WETS is going on?Weather stations, farmed land determinations, and discovering missing
August 2020 – JHWetco’s Joe Hmieleski
The following is a true story and starts from a simple question and ends down a rabbit hole. First, I am fascinated by weather and have been since I was very young. When I was a youngster, I used to set rainfall measurement devices – mostly old cups – around my house to measure the differences between precipitation around our property. While I mostly found the same precipitation amounts there were small differences that I was always found interesting.
So earlier this year I was reviewing rainfall amounts from the weather stations around Lake County during the spring and early summer. This was because I had a few projects that required farmed wetland determinations otherwise known as Agricultural Land Determinations. As you can imagine, it becomes very difficult to determine wetland vegetation when the land itself is plowed and maintained as row crops (by the way, this problem becomes more of an issue for large parts of the Midwest in agriculture production). The Natural Resources Conservation Service (NRCS), as part of the United States Department of Agriculture, is responsible for the procedure for determining wetlands on agricultural land. Without going into too much detail, the procedure relies on an annual aerial photograph (of the entire country) taken around July typically. Signatures of crop damage due to excessive moisture or poor drainage are compared to the antecedent (previous three months, or April, May, and June) precipitation.
The NRCS then uses long-term precipitation data and prepares WETS tables (more below) - an average monthly precipitation amount for an area such as Waukegan (for example, an average of 3.6 to inches of precipitation in June). One can then assess whether a month in question (say June 2020) has more or less precipitation than the average. The NRCS also calculates a 30% range higher or lower in any amount outside of that range is considered either dry (less than 30%) or wet (more than 30%). In our example here, the June 2020 precipitation amount in Waukegan (at the Waukegan Chicago regional Airport, more about this later) was measured at 3.90 inches and would be considered “normal” for a June.
The NRCS then calculates whether a April-June three month period is considered normal, wet, or dry. Aerial photographs that show crop damage under normal conditions, for more than half of the normal years, is considered a wetland signature. Confirmation of underlying hydric soils in the field is the positive criterion to be a “farmed wetland”.
A Word About WETS…
From the NRCS website:
“In order to identify the physical characteristics of wetlands adequately, the NRCS Climate Analysis for Wetlands Tables, also known as the WETS Tables, were developed. The WETS Tables define the normal range for monthly precipitation and growing season required to assess the climatic characteristics for a geographic area over a representative period of time. The Tables gives a month-by-month summary and probability analysis of temperature and precipitation. The Tables also provide the average length of the growing season using three index temperatures (32, 28, and 24 degrees Fahrenheit) at 50% and 70% probabilities.”
I digress somewhat but you needed to understand why I was looking at stations for precipitation data. If you’re reading this, you probably know that there are multiple agencies that regulate wetlands ranging from the federal (US Army Corps of Engineers-Chicago district) to the local (Lake County Stormwater Management Commission). We are lucky that the agencies defer to the NRCS for farmed land determination methodology. In this case, one would look up the closest weather station to your project and determine the “normal” years based on this procedure. That’s where the trouble started.
The LCSMC thankfully prepared a memo that specified which weather stations to use for agricultural land determinations within Lake County (see more information below). The memo specified three stations to encompass the western mostly undeveloped area (Antioch Station), a southern portion of Lake County (Barrington Station) and a Lake Michigan shoreline weather station (Waukegan Station). See Figure 1 for weather station locations.
So, what is going on here?
I was looking up the Waukegan station information and found that the weather station stopped collecting data in 2002. Thinking there was an error here, I consulted the USACE Chicago district website which provides information on agricultural land determinations and the preferred years for assessing normal conditions. The USACE-provided Waukegan station summary table ends in 2002. A check of the NRCS website showed that it lacked a Waukegan station entirely and instead added a station at the Chicago Botanic Garden in Cook County Illinois.
After a little digging, I found that the Antioch and Waukegan stations no longer collect data and Barrington is the only active station (see Table 1). Even the NRCS-added Chicago Botanic Garden site is no longer collecting data. In other words, there are no Lake County weather stations. As far as I can tell neither the USACE-Chicago District, the LCSMC, nor the NRCS have updated the weather stations in many years.
Is this a problem?
Possibly yes. Since the USACE regulates waters of the US (WOTUS) and farmlands can and often do include WOTUS, the underlying data to determine farmed wetlands is somewhat outdated. For example, the latest date indicated on the USACE-provided WETS table ends in 2002 or over 18 years ago. Similarly, the NRCS provided WETS table ends in 2014 and does not capture the last six years of data. Farmed wetlands are still being determined but the assessment is relying on older data that may have no relation to the current existing condition. Climate conditions are also showing more rainfall at different times of the year so it makes sense to try and use data representative of existing conditions.
It turns out that the NRCS compiles data from other weather sources and stations. From the NRCS website: “The data collection engine for creating WETS Tables is the Agricultural Applied Climate Information System (AgACIS). AgACIS was developed and is maintained by the NOAA Regional Climate Centers (RCCs) to manage the flow of information from climate data collectors to end users. Its main objective is to help people using climate data make management decisions.” Examining the AgACIS source, one finds two stations that may offer long-term data collection.
1. Possible Waukegan replacement: the Chicago Waukegan Regional Airport (KUGN) started collecting data in 1999 (September 1999) and maintains reliable data (see Figure 1). The station is already part of the AgACIS system and the data accessible to the public.
2. Possible Antioch replacement: while it is not in the same geographic area, the Mundelein station (at Hawthorn Woods Country Club) represents the same approximate longitude and proximity to the lake (see Figure 1). The station started collecting data in May 1999 and maintains reliable data. The station is already part of the AgACIS system and the data accessible to the public.
The AgACIS website dashboard allows users to prepare WETS table data for various stations including the two recommended above.
Joe’s Recommendations:
Weather data collection is an always changing process. This is mostly due to the costs and effort to maintain a weather station over time. Stations need periodic maintenance and upkeep all which costs money for the station owner that is mainly unreimbursed. The physical part of weather collection – the tipping bucket rain gage, or similar, often needs replacement because, you guessed it, it is exposed to the weather! Add to that the automated software that runs the device, and then the long term web uploading infrastructure, so the data becomes available for the general public, and you get a costly situation.
It seems now is the perfect time to reset the weather stations to be used for determining normal, dry and wet years under the NRCS methodology. The two replacement stations I recommend above appear to have stable funding sources and are already part of the AgACIS database that automatically calculates the monthly rainfall figures and compiles them each month year after year.
In the end, my quest for accurate rainfall data which started much earlier as a child has led me here. At least I don’t have to go out and measure rainfall data myself!
Table 1. Summary table of weather stations used as a basis for determining precipitation summaries as part of the agricultural land wetland determinations (i.e., farmed wetland determinations).
Station
SMC Guidance*
NRCS WETS Tables**
USACE-CD Website Guidance***
Antioch
7/1/1901 to 6/30/2008
Not Active
Antioch Wastewater Treatment Plant, 796 Holbeck Dr., Antioch, IL 60002
(GHCND:USC00110203)
Same as SMC; Lists Station as IL0203; WETS table ends in 2014
Same as SMC; Lists Station as IL0203; WETS table ends in 2004
Waukegan
1/1/1923 to 7/31/2002
Not Active
Radio Station WKRS, 3250 Belvidere Rd. Waukegan, 60085
(GHCND:USC00119029)
None provided
Same as SMC; Lists Station as Waukegan 2WNW IL 9029; WETS Table ends in 2002;
Barrington
11/1/1962 to Current
Active
Crabtree Nature Center, Rt. 3 Stover Rd., Barrington, Cook County, IL 60010
(GHCND:USC 00110442)
Same as SMC; Lists Station as IL0442; WETS table ends in 2014
Same as SMC; Lists Station as IL110442; WETS table ends in 2005
Chicago Botanic Garden
1/1/1981 to 6/1/2019
Not Active
Station at 1000 Lake Cook Rd., Glencoe, Cook County, Illinois
Lists Station as IL1497;
WETS table ends in 2014;
*SMC Guidance for Agricultural Land Wetland Determinations (“Farmed Wetlands”) in Lake County, Illinois, Memorandum dated March 20, 2012.
**Reference NRCS link and the Illinois Climate Zones for Wetland Determinations (October 2015). Note: the climate zone figure only shows one station within Lake County but has two others outside of the county proper but has zone extending within the County.
***Reference USACE Chicago district link for “Determinations of Wetlands on Agricultural Lands”
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