EES 21/31: Saucon Creek Watershed Project (Fall 2000)

Watersheds are terrestrial features of landscapes that contribute water to a lake or stream. Water generally travels down slope in response to gravity although pressurized springs sometimes push water in the opposite direction. Watersheds are usually defined by the surface elevation of the land over which water would flow into the receiving water body. River watersheds typically consist of a collection of sub-watersheds for tributary streams.

Along the length of a stream there will be changes to the aquatic environment because of watershed and stream processes. Natural materials are brought into the stream by tributaries and groundwater. These natural materials include: suspended particulate matter, dissolved minerals and nutrients and organic matter. Pollutants are added by discharge from pipes (called "point sources" in the environmental jargon) and from runoff of land surfaces such as farmlands, lawns, roads, and parking lots (called "non point sources").

To explore longitudinal changes in watershed characteristics, each lab section will make detailed measurements over a 100m reach of the creek at five different sites along the watershed. The data you collect today will be combined with data from the other lab sections to create a "snapshot" of the entire watershed. Data from the entire watershed will be combined, made available on the web, analyzed by students, and presented in lab reports. Additional information about how to analyze stream data is available on the Lehigh Earth Observatory (LEO) web page, at the following site http://www.leo.lehigh.edu/courses/21.html

The data will become part of a long term environmental data base on the Lehigh River Watershed managed by the Lehigh Earth Observatory (LEO).

Training goals for the field trip and beyond.

Following is a list of measurements that you will be making and interpreting over the next few weeks. Our objectives include:

1. To gather data to assess the health of a local watershed, and
2. To introduce you to real-world applications for your newly-gained environmental expertise
3. To explore longitudinal changes in watershed characteristics.

Measurements:

The parameters measured in the field at each station include the following: GPS location, weather conditions, T_air and T_water, calcium ion concentration [Ca⁺], chlorine ion concentration [Cl^-], stream width, stream depth, water velocity, bed load coarseness (bottom composition), embeddedness. Site characterization parameters include riparian zone width, riparian zone rating (streamside coverage), bank stability rating, and pool/riffle ratio. A digital image will be collected with a digital camera at each site. Water samples and macro-invertebrate samples will be collected at each site for analysis in the laboratory. The following measurements will be made in the lab from water samples collected in the field: [DO], pH, conductivity, [NO₃], [NH₄⁺], [PO₄], total particulate matter (suspended load). Invertebrate biomass and diversity will also be calculated.

Water will be collected for laboratory analysis:

• 2 BOD bottles and 1 L polycarbonate bottle should be filled prior to people entering the stream for other analysis to prevent excess sediment collection due to increased turbidity. Record the water cloudiness and the sample labels on the data sheet. Samples should be stored in a cooler on ice.

Macroinvertebrates will be collected for laboratory analysis:

• A Serber sampler will be used to collect quantitative samples of macroinvertebrates. Students collecting invertebrate samples should pick a transect upstream of where other students are working the in water. A sample should be collected approximately every meter across the stream. Record the number of samples collected. Record aquatic life observed.

Field Measurements.

• GPS: use the hand-held GPS unit to determine the latitude, longitude, and elevation of the site (Do not get the unit wet!) Also mark the location on a topographic map.
• Weather Conditions: record the current cloud cover as well as the precipitation within the last 48 hours. We need daily rainfall (12 daily totals) from the Williams Hall or Goodman weather station. Bruce Hargreaves will provide the data.

• Water & air temperature (° C): measure with a CBL; take the average measurement of several locations along site
• [Ca] (mg/L): measure with a CBL using the Ca probe
• [Cl] (mg/L): measure with a CBL using the Cl probe
• Stream width (m): measure with a tape measure along a transect perpendicular to the bank
• Stream depth (m): measure depth every meter along a transect with a meter stick
• Stream velocity (m/s): measure with a CBL using a special propeller (the propeller faces upstream) before each depth measurement at 0.6 of total depth.
• Bed load coarseness (bottom composition): estimate as a percent of each of the following types of bottom substrates: boulder, rubble, gravel, sand and fine sediment
• Embeddedness: evaluate along a transect and record on data sheet
• Site characterization (riparian zone width, riparian zone rating (streamside coverage rating), bank stability rating, pool/riffle ratio): characteristics should be assessed and recorded on data sheet
• Digital photographs: several representative images should be recorded to provide a record of the site. These images should achieve the following objectives: (1) document the sampling methods and team participants, and (2) record physical and biological characteristics such as slope, erosion, trash, and vegetation.
• Anthropogenic features: walls, dams, pollution, etc. at site.

Laboratory Measurements.

In order to minimize variation caused by instrument or calibration errors, several measurements will be conducted in the laboratory. The results will be more useful in comparing the status of the watershed if a single instrument is used in the laboratory.

Interpreting the data

GPS:

This hand-held radio receiver gets information from orbiting satellites and uses geometry and a super-accurate clock to determine its location. Latitude, longitude, and elevation will be collected at each site.

The balance between heat gain and heat loss affects water temperature (^oC). Heat gain can be from solar radiation, addition of warm rain or warm industrial or municipal discharge, and contact with warm air or warm rocks or soil. Heat loss can be from radiation to a clear sky, evaporation, and contact with cold air, cold rocks or cold soil.

Water temperature is measured in the field to help determine whether dissolved oxygen was in equilibrium or perhaps was affected by biotic processes. Changes in water temperature also indicate gradual heating from the sun, climate change as a stream flows into different latitudes, and it can be a marker for the influx of treated water (which is often warmed during treatment).

Calcium:

Ca⁺² can be leached from nearly all rocks but is much more prevalent in waters draining from limestone (CaCO₃) and gypsum (CaSO₄) regions. Calcium concentrations in waters from limestone regions range form about 30-100 mg/L. Regions where granite and siliceous sand predominate are characterized by lower concentrations.

Chloride:

Cl^- is usually associated with Na^+. It enters a stream primarily by weathering of rocks but may enter by inputs of sea salts, pollution, and runoff of deicing salts. The average [Cl^-] in unpolluted North American streams in about 7.0 mg/L.

Stream width, stream depth, and stream velocity:

These characteristics are used to calculate channel area and stream discharge values. (See below.)

Stream velocity and discharge:

The velocity or speed of the current of a stream influences both the amount of silt that is deposited and the type of river bed. Many fish and invertebrates depend on currents for feeding and respiration. Currents may also affect the distribution of fish in a stream. Velocity will be measured using a CBL with a special propeller that generates an electronic signal proportional to water velocity. Alternatively, surface velocity may be measured by timing the distance traveled by a floating object over a known length of the stream.

Discharge is the volume of water going by a set point in a given time. Discharge will affect turbidity, total dissolved solids, and if it is very high can reduce the fauna in an area. Biologically, it is probably less significant when it varies or is very slow for long periods of time. This is especially true when a stream has no pools to tide fish over until higher water comes. High discharges will promote spawning in some fish while in others it will destroy nests and young fry. To estimate discharge, the water velocity and depth will be measured every meter across the width of the stream so that total cross-sectional area can be estimated.

Bed load coarseness (Bottom composition):

The bottom composition can greatly affect the ecological processes that occur along the stream. Boulder substrate provides channel stability, macro- and micro-habitat for many aquatic species, and fish cover. Rubble stabilizes the stream bottom, provides habitat for fish rearing, and is the substrate for some aquatic invertebrates. Sand and fine sediment decrease permeability of spawning gravels and can plug interstices and there by interfere with water flow.

Bed load coarseness is determined by assigning percent values to the following 4 substrate types.

Embeddedness:

Embeddedness is the degree to which larger particles (boulder, rubble, or gravel) are surrounded or covered by fine sediment. The embeddedness also affects the ecology by determining the channel substrate’s suitability for spawning, egg incubation, and habitat for aquatic invertebrates and young overwintering fish. As the percent of embeddedness increases, the biotic productivity decreases. Use the following table to rate the embeddedness:

(sediment = particles <4.7 mm in diameter)

Bank stability:

Bank conditions at each end of a transect are rated either as "stable" or "unstable". An unstable rating is given if there is any evidence of soil sloughing within the past year. The number of stable banks for each site is recorded as 0, 1 or 2.

Riparian zone:

The riparian zone (streamside cover) is the vegetative portion of the streamside environment. Streamside vegetation reduces both sediment and nutrient transport from the landscape into the stream. Shading by the vegetation can prevent extreme temperatures changes (lower max. in summer and higher min. in winter).

The width of the riparian zone will be measured using a tape measure. A riparian zone at each station will be rated on a scale from 4 (highest) to 1 (lowest) according to the descriptions provided in the table that follows. Functionally, the rating considers all material (organic and inorganic) on or above the streambank that offers streambank protection from erosion, stream shading, escape cover, and resting security or fish.

Water surface characterization (pool/riffle ratio):

Water surface should be recognized as existing in 2 classes: pools and riffles. In general, parts of the channel where the water flows more slowly and is deeper than in surrounding portions are called pools. Conversely, the faster moving, more shallow portions are called riffles. Pools and riffles are usually intermixed along a single transect.

Observe the pools and riffles along the transect and estimate the percent of each type of surface characterization. The pool-riffle ratio will be estimated for each transect by dividing the percent of riffles by the percent of pools. The pool-riffle ratio is used to predict the stream’s capacity to provide resting and feeding pools for fish, and riffles to produce food and support spawning activities. The optimum ratio is 1 to 1. Evaluate bottom characteristics for both riffles and pools.

Dissolved oxygen:

Dissolved oxygen concentration (mg/L) is affected by contact with the atmosphere, water temperature (which inversely affects solubility), and biological processes (respiration by organisms consumes oxygen while photosynthesis produces oxygen).

Dissolved oxygen is used as an indicator of water quality because many types of pollution will cause excess bacterial respiration (and low [DO]). Excess heating of the water, either by discharge or by removal of shade trees along the banks of a stream, will cause the water to have lower levels of oxygen as it equilibrates to lower oxygen solubility.

When water is well mixed with air, the dissolved oxygen concentration [DO] approaches the solubility value and the water is considered 100% saturated. Use a nomograph to convert the water temperature measured at each station and lab-measured [DO] into percent saturation. This will help determine if changes in [DO] represent biological processes or simply equilibration to a new temperature.

The pH represents acidity where numbers less than 7 are considered acidic and greater than 7 basic at room temperature. Technically, pH units are calculated as 1/log([H⁺]). Environmental sources of acid include sulfuric and nitric acids in rainfall and waste from mining (e.g. from coal containing sulfur). Sources of bases include dissolved minerals from carbonate rocks. Dissolved minerals in the water affect pH. Sources of dissolved minerals in the watershed include pollution in rainfall, rock weathering (especially carbonate rocks), road salt, and discharges of treated wastewater.

Conductivity:

Conductivity (m S/cm at 25^oC) measures how easily electric current is conducted through a solution. It can be used as an index of dissolved mineral concentration because dissolved metals are present in water as cations (having positive charges) and anions (having negative charges). Conductivity indicates the approximate amount of dissolved solids present in the water, which may reflect rock chemical weathering, runoff of road salt used for ice removal in winter, as well as runoff of nutrients from lawns, golf courses, and agricultural lands.

Nutrients:

Nutrient data for g/L N (in the form of nitrate) and g/L P (soluble reactive phosphorus) can be combined with volume flow rate to yield the river or tributary load (g/s) which indicates the degree of pollution caused by non-point source runoff from lawns and agricultural lands, and point-discharge from sewage treatment plants

Nutrient loading: Changes in the concentration of substances in natural waters may reveal natural or anthropogenic processes in the watershed. The mixing of the way-water from the stream with water from its tributaries complicates interpreting such changes. An analysis of "loading" from sources in the watershed can help unravel the complexities. This approach is an important part of governmental management of environmental quality and thus of pollution management. Sources originating from a pipe or channel are called "point sources" while sources that cover a broad area (e.g. for atmospheric deposition, runoff from fields or roadways) are called "non-point sources". In your analysis below you can look at loading of the stream from all sources by multiplying concentration (nutrients) by flow rate at each station to get amount delivered per second and then compare upstream to downstream values. When you treat loading this way the point and non-point sources are combined. Note that a cubic meter is 100 (10²) centimeters on each side and has a volume equivalent to 10⁶ milliliters (same as cubic centimeters) or 10³ liters.

Diversity:

Many forms of stress tend to reduce biodiversity by making the environment unsuitable for some species or by giving other species a competitive advantage. Species diversity is a function of the number of species present and the distribution of individuals among the species. Diversity indices provide means for measuring the quality of an environment by measuring the effect of induced stress on the structure of a community of macroinvertebrates. Macroinvertebrates are commonly used an "environmental indicators" because their community structures are often impacted by environmental disturbance. Therefore, macroinvertebrate diversity can often reflect the heath of the larger environment.

The use of diversity indices is based on the observed phenomenon that relatively undisturbed environments support communities that have large numbers of species, while no individual species exist in overwhelming abundance. If the species in such a community are rated on the basis of their numerical abundance, there will be relatively few species with large numbers of individuals and large numbers of species represented by only a few individuals.

The Shannon-Weaver index will be used to calculate the diversity of the macroinvertebrates collected at each site. A greater value for the diversity index indicates a more diverse community of macroinvertebrates.