The second half of the Arkansas Forestry and Drinking Water Collaborative’s vision statement is, ‘…Clean Drinking Water’. This raises the question of what constitutes clean drinking water with respect to forestry. Water quality, according to the United States Geological Survey (https://water.usgs.gov/edu/waterquality.html) can be thought of as ‘a measure of the suitability of water for a particular use based on selected physical, chemical, and biological characteristics’. There is no absolute scale for water quality without an intended use of the water. For drinking water, we want water that is free of pathogenic (disease causing) organisms, toxins, undesirable taste and odor and has a pleasant appearance.
The United States Environmental Protection Agency regulates 90 contaminants (https://www.epa.gov/ground-water-and-drinking-water/national-primary-drinking-water-regulations) that have direct impact on human health. These are called the National Primary Drinking Water Standards. For each of the primary contaminants, a maximum contaminant level (MCL) is set. Drinking Water from public systems is not allowed to exceed any of these 90 standards. There are also an additional 15 contaminants (https://www.epa.gov/dwstandardsregulations/secondary-drinking-water-standards-guidance-nuisance-chemicals) that impact the aesthetic quality of water or may impact the operation of water treatment equipment. These 15 are referred to as secondary water quality standards. Water utilities strive to meet all 105 of these water quality standards.
But the description of clean water above is for water that has been through a sophisticated treatment process. Ambient water, water in the natural system of streams and lakes or groundwater, generally does not meet all 105 drinking water standards. There may be a few places in remote wilderness where a person can kneel down and drink from a stream. But those places are few and far between. You never know what is going on upstream just around the bend.
Water utilities refer to the ambient water as ‘raw’ water. That is water that has not yet been treated. A utility wants raw water that can be safely treated at a reasonable cost. Certain characteristics of water can make it difficult to treat. Algae can at times impart taste and odors into the water. That taste and odor is usually not unhealthy, but it becomes unpleasant for drinking. Taste and odor are extremely difficult to remove from water through the normal treatment processes. Some alga also at times forms toxic compounds. These algae are referred to as Harmful Algae Blooms (HABs). Algae blooms are difficult to manage and treat for because of their temporary nature. A bloom can show up overnight, then be gone the next night. Algae toxins can be treated, but it difficult and expensive. And with our current testing methods, the toxin may already be in the system before its presence is known. Luckly, HABs have been rare in Arkansas. Algae grow in response to many environmental conditions. But a certain amount of fertilizer (nitrogen or phosphorus) is required for their growth in any situation. So, a raw water low in fertilizer is desired.
Organic carbon also causes water treatment woes. When organic material is treated with disinfectant, the process forms by-products. Some of those by-products may be carcinogens. While these by-products can be treated for, it is better to not have them in the first place. The best treatment in this case is prevention. So, the raw water should have a low concentration of organic carbon.
Water utilities also have to remove turbidity (cloudiness) from the water as well as to remove all of the suspended solid particles. The removed particles form what is called water treatment residuals. Water treatment residuals have to be disposed of in an acceptable manner.
A water utility then would likely think they had clean raw water if that water was relatively clear (low turbidity), had a low concentration of nitrogen and phosphorus, little nuisance algae, little organic carbon, and few suspended solids. They also want good buffers between them and any potential source of contamination such as spills, leaking storage tanks, waste water discharges etc.
The quality of water in a stream or lake is directly related to the characteristics of the watershed tributary to that stream or lake. Land use (urban, forest, farming, residential etc.) has an impact on water quality as well. Of the land uses common in Arkansas, well managed forest provides water that most closely matches the needs of the water utility. The connection of forestry to clean water is a natural.