Originally Posted on: September 15th, 2015
Almost 750 million people around the world do not have access to safe drinking water. Almost none of these people live in the United States. The reason? The United States has robust water treatment and distribution infrastructure, along with highly-trained engineers, scientists, and water treatment plant operators focused on municipal water supplies. A person can travel almost anywhere in the United States and drink the water without giving a second thought to its safety.
This is not to say that safe water comes easy. Many municipal water supplies here in Iowa have challenges related to source water quality—pesticides, nitrate, and bacteria can be present in the lakes, streams, and wells that are used to supply our drinking water. And many community water supplies, especially in Northwest Iowa, are vulnerable to drought.
Scientists at IIHR are working with municipal water supply operators in several Iowa cities to help bring safe and reliable supplies of drinking water to those communities.
Boone, Iowa draws its supply from several shallow wells in the Des Moines River valley. Almost every year the Des Moines River has nitrate concentrations that far exceed the safe drinking water limit. How much of this nitrate intrudes into the Boone wells varies from year to year. Boone well water nitrate has been higher this year than most other years.
What are the mechanisms driving well water nitrate in the Boone wells? Water temperature and river stage, as well as river nitrate, probably all contribute. Understanding these processes is where IIHR comes in. IIHR scientists are deploying continuous, real-time nitrate sensors in one of the wells and the adjacent river to see how the well water responds to varying river conditions. Boone staff will have access to this data so they can better understand their system and develop efficient blending strategies for the wells. IIHR researchers will gain insights into processes controlling nitrate levels in the floodplain and alluvial valley.
Northwest Iowa Alluvial Wells
There’s no other water system like Rural Water System Number 1 near Hospers in far northwestern Iowa. The utility has fewer than 2000 customers but treats an enormous amount of water—almost 72,000 gallons per month per customer. Why? The system also has many non-human customers, including hundreds of thousands of cattle, hogs, chickens, and turkeys that consume the vast majority of the treated water. One dairy cow requires 55 gallons of water per day; a meat chicken ¾ of a gallon.
The utility draws water from wells in the Floyd River valley. Intense crop and livestock production create a nutrient-rich environment in the area. The water treatment plant has no nitrate-removal capability, so the lead operator has devised a clever scheme of perennial plants, wetlands, and holding ponds to soak up excess nitrate before it gets to the wells. The treated drinking water remains safe to drink for both people and animals.
IIHR Research Engineer Keith Schilling is creating an experimental plan to assess the effect of these innovative strategies. Determining the mechanisms and quantifying their effects is crucial if these ideas are to be used by other similarly-affected water systems.
IIHR/Iowa Geological Survey hydrologists Mike Gannon and Jason Vogelgesang have also been busy in northwest Iowa. They are working on a hydrologic investigation to evaluate the impact of a water recharge basin constructed by Rock Valley Rural Water District (RVRWD) in Sioux County. This study will test water quality of surface water, on-site production wells, and shallow monitoring wells. Researchers will develop a calibrated groundwater model to evaluate water storage and potential contaminants.
Gannon and Vogelgesang also completed a drought assessment for the City of Sioux Center alluvial wellfield. They calibrated a groundwater flow model to quantify the storage potential of low head dams and their ability to induce water recharge of the city’s wells. They are also using the calibrated flow model to evaluate various other drought strategies to enhance both aquifer storage and induced recharge.
Municipal water supply systems are not designed for an average water use day. Rather, they are based on peak periods—days of maximum water use in the summer or when fighting a major fire. Many times strategic infrastructure plans for a water utility look 30 or more years into the future, estimating population growth and economic activity.
More and more, treatment plant operators understand their systems also need to be designed for peak water-quality days—when source water quality is at its worst.
Ottumwa is one such system. The city uses Des Moines River water as its source supply. Similar to Boone, nitrate levels are high in the river almost every year. Moving forward with a strategic plan requires an understanding of future water quality.
IIHR water quality experts Antonio Arenas Amado and Keith Schilling recently received funding from Stanley Consultants Inc. to estimate future nitrate levels in the Des Moines River at Ottumwa. This information will inform the city’s waterworks about what can be expected in the coming decades, and what strategies will be necessary to provide safe drinking water to Ottumwa’s citizens.
Safe drinking water is a fundamental requirement for modern society. A city and its economy cannot function if the safety of the water is in doubt. IIHR scientists are committed to this mission for Iowa’s citizens, now and into the future.