Twin Lakes Watershed Data

How will we know if our efforts are actually improving water quality in the Twin Lakes watershed? We need data showing nitrogen and phosphorus levels in the watershed’s streams at the start of the project, which we will compare to data we gather each year as the project progresses to look for changes in nitrogen, phosphorus, and other pollutants.

LPSNRD and NDEE began collecting water samples from three streams in the watershed in May 2021. We sample each week during May and June, biweekly July through September, and after rain events.

Field Data

PH

What is it? How acidic or basic the water is. Neutral water has a pH of 7.0. A pH of less than 7.0 is acidic; common acidic liquids include lemon juice, vinegar, and soda. A pH of greater than 7.0 is basic; basic liquids you might be familiar with are laundry detergent, soap, and drain cleaner. pH is measured in standard units, which don’t get an abbreviation next to the number.

What does it mean? In nature, water is rarely perfectly neutral, so measurements slightly above or below 7.0 are not unusual. How close the water is to 7.0, and whether it’s a little on the acidic side or the basic side, determine what kinds of organisms (plants, animals, etc.) can live in the water. Surface water in this part of the state tends to measure a little higher than 7.0, and our sample sites are no different.

Why isn’t the water a perfect 7.0? Streams carry much more than just water, even if you can’t see it. Dissolved minerals, decaying organic matter, and pollutants, for example, all affect water’s pH. Some of those things are naturally occurring, and some come from human activities.

2021 Sampling Data

Seasonal average = 7.72

Seasonal average = 7.65

Seasonal average = 7.84

Temperature

What is it? How hot or cold the water is. Water that seeps out of the ground tends to be colder than water that falls as rain and runs off the land surface into a stream. A stream flowing through an area with well-vegetated banks will be cooler than a stream whose banks have no vegetation. Temperature is measured in degrees Celsius (° C).

What does it mean? Some organisms like warm water, and some prefer cooler water. The green algae we often see on ponds in the summer, for example, thrive at higher water temperatures. Fish such as trout are happy in cold-water streams.

2021 Sampling Data

Seasonal average = 15.9° C (about 60° F)

Seasonal average = 16.3° C (about 61° F)

Seasonal average = 16.8° C (about 62° F)

Lab Data

Nitrate-Nitrogen

What is it? Nitrogen occurs naturally in soils and is a major component of fertilizers and other chemicals. Plants require nitrogen for growth.

What does it mean? High nitrate-nitrogen in water can cause health problems for humans and aquatic life. Excess nitrate-nitrogen in Nebraska streams, lakes, and groundwater comes from fertilizer runoff or percolation from agricultural fields.

Phosphorus

What is it? Like nitrogen, some phosphorus occurs naturally in soils, but generally in concentrations too low to support intensive crop production. Phosphorus is a major component of fertilizers and pesticides.

What does it mean? Excess phosphorus in streams and lakes promotes the growth of toxic algae blooms, which can close beaches and kill aquatic life. Phosphorus makes its way into our waters through fertilizer and chemical runoff from agricultural fields and residential lawns.

Pesticides (Atrazine)

What is it? Agricultural producers apply various pesticides and herbicides to crops during the growing season. Atrazine is an herbicide used to combat certain weeds. Once widely used on both agricultural fields and residential lawns, use is now more restricted.

What does it mean? Atrazine and other chemicals can cause health problems for humans and aquatic life. These chemicals run off from agricultural fields during rain events or irrigation and flow into streams and lakes.

Bacteria (Total Coliform)

What is it? Coliform bacteria live in the intestines of animals, including humans! Different animals each have different varieties of coliform bacteria that are unique to them. They end up in the environment when an animal poops; as feces break down, rain events can wash those bacteria into streams and lakes. Coliform are measured with the most probable number per 100 milliliters (MPN/100mL). “Most probable number” indicates the most likely number of colonies of bacteria in the sample, which represents the number of bacteria in the stream.

What does it mean?Everybody poops! Cows, deer, raccoons, turkeys—you name it. Large numbers of coliform bacteria in water can make you sick, if you ingest the water. Bacteria in water can come from runoff, but also from septic drainfields that are too close to a stream or to groundwater.

2021 Sampling Data

Seasonal average = 2,001.8 MPN/100mL

Seasonal average = 1,816.7 MPN/100mL

Seasonal average = 1,819.5 MPN/100mL

Orange markers on the graphs mean that the value you see comes from the diluted sample, rather than the full-strength sample. This happens when the full-strength sample has so many bacteria in it that it’s off the charts. In those cases, we use the diluted sample instead to get a bacteria count.