Lab 3: Observations in the field - water quality of Elmwood Creek South of the UNO campus.

Pedagogic objective: Data play a crucial role in science. Without it, one may be guilty of arm waving, of mere speculation without supporting evidence. Data can be thought of as the ground your model stands on. Even the most exquisite of computer models needs good input - otherwise, garbage in garbage out. In earth system science gathering data often means doing field work. The purpose of this lab is to give you experience with observing and sampling in the field. The data you gather in this lab will be used in a subsequent lab.

Scientific objective: The objective of this lab is to understand the hydrologic dynamics and water chemistry of a segment of Elmwood Creek between Dodge and Pacific Streets. What factors influence the flow of water through the creek and the chemistry of that water?

Some background information on water quality: There are actually many measures of water quality. Due to time and cost limits we will only use a few.

Temperature: A variation in temperature more indirectly influence water quality. A warm glass of water can quench your thirst. However, in general the warmer the water the more dissolved material it holds and the more microbes that can grow in it. So temperature very much influences other quality indicators, and it is necessary to measure it. What influences the temperature? The interchange of heat between the atmosphere and surface waters, and the mixing in of a groundwater source with its temperature are two such factors. Waterontheweb site discussion of the importance of T.

pH: Technically, this is a measure of the balance between hydrogen ions and hydroxide ions (OH) in the water. We know it as acidity. Acids have a prevalence of positive hydrogen ions and bases have a prevalence of negative hydroxide ions. Surface waters can vary significantly in their pH. Contact with certan types of rocks, such as limestone, can make them more basic, while other types of rocks such as granite, can make them more acidic. Acid mine runoff is an example of surface water with very high acidities. In addition, organic activity can influence acidity in complex ways, but commonly by influencing carbon dioxide levels in the water (the carbon dioxide dissolved in the water produces a weak carbonic acid). Waterontheweb site discussion of what influences water pH.

TDS: TDS stands for total dissolved solids. It is a measure of how much material ionic material is dissolved in the water (i.e. a measure of its salinity). In general, the higher the TDS the lower the quality of the water. This is a very broad brush descriptor of water chemistry. In addition to knowing how much material is dissolved in the water, you might want to know what is dissolved in the water. TDS is controlled by many factors, including pH, temperature, and the type of material the rock comes in contact with (and how soluble that material is). In general, the longer the water is in contact with sol and rocks the higher the TDS (up to a saturation point). Evaporation can also increase TDS, by selectively leaving the dissolved salts behind in the remaining water. Waterontheweb site discussion of TDS and conductivity.

DO: DO stands for dissolved oxygen. Atmospheric gases are dissolved in surface waters. This DO is what fish breath. In anoxic waters (water without DO), fish and other aquatic organisms requiring oxygen perish. Oxygen diffuses from the atmosphere into the water at the water surface. The more agitated the water's surface, the more diffusion that takes place (due to the increased surface area). Waves, rapids, waterfalls and riffles also serve to agitate the water.The counter balance to that is largely the microbial activity taking place in the water. If water has organic material in it, then bacteria will eat that organic material and use up the oxygen as they do so. Slow moving and/or organic rich water is usually low in DO. Waterontheweb site discussion of DO.

All of these can be measured using various meters in the field. Which ones you will keep track of depend on how many meters we have. The water samples we will take will be analyzed by a chemistry class for other water quality indicators, which we will disucss later. In a subsequent lab we will then take that data and work with it.

Preparation for field work: You should take the airphotos and maps provided and familiarize yourself with the study area. First orient yourself by identifying major features such as the UNO parking garage. Clicking on either of the images below will produce a larger version of that image (it may be slow to load with some connections). Then identify on the air photos any features that you think may influence the water flow and chemistry. Think of where would be good places to take water samples and observations.

Safety considerations: Safety is an important issue when doing field work. In this particular study beware of poison ivy. It also will be helpful to wear good boots, or at least sneakers. Also, you may have to do some climbing up and down the stream banks. Be careful. There is not data worth getting hurt for.

Suggestions for sampling plan: Your sampling plan is what determines why you sample or take observations were you do. There are many types of sampling plans. For this project you could use a systematic plan of consistent sampling spacing - for example, sample every ten meters down stream. You could also have a computer randomly choose locations along the length of the stream to sample. Both of these approaches could have their advantages and disadvantages depending on the specific question you are interested in answering. We will use what is called an opportunistic sampling plan, one guided by 'opportunity'. For example, if there is an area of more turbulent water, then you have the opportunity to sample just above and below this stretch of water and see what effect the turbulence has on various parameters. Where can you actually physically take samples also determines your opportunities (e.g. without a boat the middle of the small pond is inaccessible, but you can sample from the shoreline).

GPS and location of sampling sites: For comparison and mapping purposes you need to locate the sample sites in the field. This is much easier than it used to be. GPS stands for global positioning system, and the off the counter GPS units offer a location accuracy of tens of feet or better. This will be adequate for our purposes. There are a variety of conventions for locating yourself on the surface of the earth. Two major ones are by latitude-longitude, and UTM, and your GPS unit will provide your position in both of these. We will use latitude and longitude for multiple reasons. The traditional units of a latitude and longitude measurement are degrees, minutes and seconds. However, we will use decimal degrees, where the minutes and seconds have been converted to a fraction of a degree. To convert from one to the other simply remember that there are 60 seconds in a minute and sixty minutes in a degree.

Organization: We will start off by the small pond on the golf course, and after some discussion and demonstration of how to use the equipment we will send you off in groups to take measurements and samples from different parts of the stream. Each group should get at least 5 water samples. It will help to have a clipboard.

Final lab products:


Some background information and pictures of Elmwood Park.