Deborah L. Turnbull
The objective of this unit is to teach students the importance of knowing the watershed in which they live. The unit is divided into four parts; watershed, hydrologic cycle, surface water and ground water. The strategy for each section is to provide teachers with background information and then to suggest in-the-classroom, in-the-playground, and in-the-field curricula units to enhance classroom lectures. A Teacher’s Box accompanies this unit and contains a slide show of the flora, fauna, chemistry, geology, and land use of a local river, along with maps of importance.
Watershed
Watershed is a relatively new word to many people. It refers to an area drained by a stream or river. Think of a mud puddle in your yard. The area of yard it drains is termed its watershed and may be an acre or so large. On a bigger scale, let’s look at the Quinnipiac River, a river familiar to all of us who live in New Haven. It drains a watershed of some 363 square miles.(1) On an even grander scale, the Mississippi River drains a watershed of 1,243,000 square miles. These large watersheds are made up of many smaller ones, such as your back yard. The Muddy River, a tributary of the Quinnipiac River, will be the river we will focus on in this unit, along with its watershed of some 18 square miles.(2)
Figure 1—Watershed
(figure available in print form)
The watershed you live in may include farmland, urban development, or industrial plants and may be flat, hilly, or mountainous. You, along with other people, plants, and animals, are all part of the watershed community. All our lives depend on the watershed, on water, and we in turn influence what happens to the watershed. What people do to the water upstream affects you and what you do to the water you live by affects the larger watershed downstream. Figure 1 illustrates a typical watershed.
After the initial introduction, explore the school site with your students to investigate the flow of surface water on the school grounds as related to the larger concept of watershed. Curriculum Unit #1,
The School Site Watershed: Puddle Study
, has been designed to accompany this portion of the unit. It includes a lesson on developing a key and a mapping activity and is located at the end of this unit. Also, topographic maps of the Branford and Wallingford quadrangles, the two quadrangles that the Muddy River runs through, can be found in the Teacher’s Box. You may wish to teach a lesson in reading and interpretation of map symbols. It could be a lesson in math taught by discussing height and depth with the use of contour lines. Use the map to locate the watershed of the school from the slopes, hills, and mountains of the area which drains down into it. If your school is located in a different quadrangle, use of the Teacher’s Resource section of this unit will help you locate it. You will find wetland areas on your map which will help give your students a sense of how water-rich our region is. This understanding should be balanced with an understanding of the fragile nature of water quality.
Hydrologic Cycle
The hydrologic cycle is a term referring to the circulation of water between land masses, the ocean and the atmosphere. Water vapor condenses in the atmosphere and falls to the earth in the form of rain, snow or sleet. Almost all of the water seeps into the earth. Part of this portion remains as ground water, part flows through to eventually reach streams, and much is evapotranspirated by plants. A small part flows over the land surface as surface flow. When this part evaporates, as well as when the flowthrough portion is evapotranspirated, the water returns to the atmosphere to complete the cycle. Please see Figure 2 for an illustration of the hydrologic cycle.
Figure 2—The Hydrologic Cycle
(figure available in print form)
The hydrologic cycle in a drainage basin can be described by a water budget as the total amount available and as receipts and disbursements of water. The receipts of water in the basin consist of the various forms of precipitation. Some 91% of the water that falls to earth infiltrates into the ground. Most of this does not become part of the ground water, which is water in the saturated zone. The saturated zone is the subsurface zone in which all open spaces are filled with water. The water table is the upper limit of this zone.(3) Disbursements consist mostly of the evapotranspiration of this infiltrated water, stream flow out of the water shed and ground water flow (which is small compared to the other two). The budget always balances although the amounts in each element of the budget may vary somewhat from year to year. The approximate amounts involved in each element for the Quinnipiac River basin are shown in Figure 2. These amounts are derived by measuring an area of land times the thickness of the layer of water. The figures are the annual water budget. The most recent set of data show that the mean monthly precipitation is fairly uniform throughout the year, the average being 3.95 inches per month. Mean monthly runoff follows a seasonal cycle with maximum amounts in the spring and minimal amounts in the late summer. The combination of causes for this include increased evapotranspiration and evaporation during the summer, storage of water as ice and snow during the winter, and increased ground water runoff in the spring. (4)
Water moving through the hydrologic cycle has its composition altered by interaction with the chemical and physical properties of the medium through which it moves. Precipitation dissolved particles and gases from the atmosphere. So, if rain moves through soot and motor exhaust, one result will be that it will pick up sulfate and nitrate ions and fall to the land surface as acid rain. Surface waters that move through the farm lands will pick up pesticides and fertilizers and may in turn add to the eutrification of the pond or lake into which the water flows. Ground water naturally is more mineralized than surface water due to its underground storage and longer contact with rock.
After introducing the hydrologic cycle to your students, here are a few ideas to help you illustrate the basic concepts: 1. As part of Curriculum Unit #2, have students visit the four sites marked on the surficial maps of the Branford and Wallingford quadrangles along the Muddy River, noting land use and its possible effects on the river’s water quality; 2. Obtain the film “Buttercup” from ACES (listed in your Teacher Resource section) and have students list all the uses of water through which “Buttercup” passes; 3. Have students use surficial geology maps of the Wallingford and Branford quadrangles to chart the flow of the Muddy River and the various types of land use it passes through and possible effects on the quality of the river water.
The average family of four uses 255 gallons per day of water for their household.(5) A more thorough discussion of water use and ideas for water-saving devices and appliances for your home can be found in the booklet “You Can Conserve Water,” which can be found in the Teacher’s Box.
Surface Water
Almost all water that appears in streams, lakes, ponds and rivers has also participated in underground flow. Water reaches streams by the flow of water below ground, termed flowthrough, for the most part, and also by the flow of ground water, a much slower process. About 9% of the water that arrives to the earth by precipitation joins streams by direct flow over the land surface.(6)
Streams will be the focus of this portion of the unit. The stream is a dynamic, shifting habitat which is subject to greater changes than the larger bodies of water such as lakes. And, in the stream itself, there are a variety of habitats or niches depending on its physical characteristics. The location of the stream and speed of the flow will determine whether the bottom will be composed of silt, sand, rubble, or bedrock. The nature of this substratum will determine the types of plants and animals that live there. The amount of streamflow passing any point within a basin varies continuously depending on season, size of the stream drainage basin, precipitation, evapotranspiration, surface and ground water storage, topography, and the influence of man on the stream and surrounding areas. Streamflow data is produced by the U.S. Geologic Survey and is used for determination of water supply potential and to estimate mean annual flow, duration of flow, and magnitude and frequency of floods.
Eventually streams run into a larger body of water such as a pond, lake, river or another stream. Bodies of freshwater with increasing size to deeper waters are creek, brook, stream and river. Conditions change along the length of the stream as it progresses from the cold, swift-moving headwaters to the slow-moving muddy waters of the mouth. In the small space of, say, 6 feet of stream length, one can find rapids or riffles over hard or rocky bottoms and calm pools with muddy bottoms. The plant and animal species found in these two environments will be very different.(7)
Curriculum Unit #2 has been designed to accompany the surface water section. This curriculum, entitled
Stream Exploration
, is a field trip where students will study a site or sites along the Muddy River (or another river), analyzing flora and fauna and their interactions, water chemistry, geological history from maps and observations, physical stream environment, and land use. Geological background for teachers will be covered in the Ground Water section of this unit.
Each organism that lives in the stream is specially adapted to its environment. The most diverse environments, and hence the place where you will find species of organisms, is that of the gravel and rubble-bottom portion of the stream. Due to the turbulent waters running over this type of bottom, more oxygen is mixed from the atmosphere, and thus the area can support many types of organisms.
Pelagic organisms which float or swim freely are phytoplankton, zooplankton, insects, fish and amphibians. Phytoplankton, a producer in the stream environment, are tiny plants that live near the surface using energy from the sun, carbon dioxide, and nutrients, such as phosphates and nitrates, to produce their own food. You can either purchase a phytoplankton net or make one by tying a knot in the tubular section of a stocking and securing the other end around a circularly-shaped coat hanger. Hold the net at the riffle area (an area over the gravel section of a stream) for 10 minutes to collect the plankton as they pass through and view them under a compound microscope. The zooplankton, or the animal portion of the plankton population that float or weakly swim near the surface of the stream, can be collected in the same manner. Zooplankton and phytoplankton species, along with all other plants and animals mentioned in this unit, can be identified using the book,
A Field Guide to the Study of Fresh Water Biology
, listed in your Teacher Bibliography section.
The largest and most popular of the stream animals are the fish and are the only vertebrates that live directly in the water. They can be collected by direct netting or by turning over rocks upstream and holding the net downstream while another person walks through the stream, moving the fish into the met.
You will find most amphibians living in the slow-moving pools alongside the riffle areas or on the banks of the stream.
Bottom organisms can be found attached to or living under the rocks. Algaes, such as blue-green algaes, can be found attached to rocks. Also, larger water plants, such as
Elodea
, can be found. Many insects spend their larval stages under rocks and invertebrates, such as clams, snails, and crayfish can be found.
Surface organisms, such as water spiders and water beetles, can be seen floating or gliding along the water surface tension.
And don’t forget to look for clues of the animals who visit the stream habitat. Look for footprints of mammals, such as raccoon, fox, muskrat, and a variety of bird species.
Have your students do a sketch map which should include: river course, width and flow, shallow and deep sections, river bed conditions (sand, clay, gravel, boulder), eddies in stream flow, bank conditions (slope, composition, undercutting), river obstructions and extent of flood plain. Flood plain is that area of land adjacent to the stream that is flooded by the stream during especially high waters.
Also, look for human impact on the area, such as water impoundment, recreational use, vicinity to farm lands, runoff of water from roads, channeling of stream, etc.
To check for water quality, sample at least the first five parameters with Hach or LaMotte test kits: dissolved oxygen, carbon dioxide, pH, temperature, density, dissolved solids, iron, manganese, chloride, nitrate, hardness, trace elements, bacteria, sediment and turbidity. Table 1 illustrates the source and significance of the first five parameters. A discussion of the others can be found in the U.S. Geological Survey
Water Resources, Quinnipiac River Basin
, listed in the Teacher Bibliography section.
If the minimum flow of a stream is inadequate for a projected rate of use, a dam and a reservoir may be constructed to store water for subsequent release. An example of this can be seen on the Muddy River at the Mackensie or Big Pine Reservoir. The amount of storage provided here depends on the amount of water needed, loss due to evaporation, and seepage from the reservoir into ground water storage.
TABLE 1 SOURCE AND SIGNIFICANCE OF SOME COMMON CONSTITUENTS OF WATER
(figure available in print form)
Floods can and have occurred in every month of the year in the Muddy River and Quinnipiac River Basins. Due to rapid snowmelt and rain, however, flooding is most common in the spring. A study on the magnitude, frequency of flood flows, and probability of occurrence can be found in the U.S.G.S. publication,
Water Resources, Quinnipiac River Basin
.
Ground Water
Ground water, that water that percolates to the water table, is water in the saturated zone. The geological formation that contains sufficient saturated, permeable materials to yield significant quantities of water for use is termed an aquifer. We will look at ground water from the perspective of its availability for human use depending on its medium of storage—bedrock, stratified drift or till. These geological terms, along with a discussion of the geological history of the land surrounding the Muddy River, follows. Curriculum Unit #2 contains areas of geologic investigation for you to visit while on a field trip with your students.
The deeper we go into geologic history, the harder it is to decipher past events. The world itself is some 4,600 million years old. The oldest rocks in North America are found in Ontario and Minnesota and are about 3,500 million years old.(8) The rocks in the Eastern and Western Connecticut highlands are about 500 million years old, and the Connecticut Valley was formed about 100 million years ago when the Eastern and Western highlands were pulled apart during the formation of the Atlantic Ocean. The Quinnipiac River basin, and hence the Muddy River basin, lie in the Connecticut Valley lowland area.
The term bedrock refers to the solid rock that forms the Earth’s crust. It is sometimes exposed at the surface for us to see, but more commonly buried beneath deposits. The bedrock in the Connecticut Valley consists of sedimentary and igneous bedrock units with some metamorphic units at the far Eastern and Western perimeters. Sedimentary rocks are formed of sediments originating from the weathering of other rocks and can be transported by water. The types of sedimentary rocks found in the Quinnipiac River basin are sandstone, siltstone and shale, with lesser amounts of conglomerate and limestone. Igneous rocks are formed by solidification of molten or partially molten magma and in this basin consist principally of basalt (or diabase) units and are interbedded with, and include, the sedimentary rocks. To the Eastern and Western boundaries, metamorphic bedrock underlies the basin. Metamorphic rock forms in the solid state by heat and pressure from other already existing rocks and here consists of gneiss’s shist and phyllite. The Connecticut Valley Urban Area project maps of the Wallingford and Branford quadrangles, provided for you in the Teacher’s Box, show the configuration of the bedrock surface if all Earth materials covering it were removed. The surficial maps of both quadrangles show areas of exposed bedrocks that are of potential interest for field trips for you and your students.(9)
Bedrock aquifers underlie both quadrangles and include sedimentary, igneous and metamorphic rock types. Bedrock aquifers are sources of water for many homes that are not connected to public water supplies. Due to their relative porosity, sedimentary rock aquifers are the most productive, followed by igneous and then metamorphic rock aquifers.
The millions of years following the formation of the Connecticut Valley were characterized by erosion and a rising of the land. Due to this erosion, a blanket of eroded rock covered much of Connecticut. It is probable that the Muddy River existed at this time. The Muddy River slows through the Wallingford and Branford quadrangles through areas of lesser elevation. The river was present here before glaciation and apparently took the path of least resistance draining the surrounding land of some 18 square miles on its way down to its intersection with the Quinnipiac River.(10)
Around 10 million years ago, the climate was getting colder and ice was accumulating in Antarctica. Giant ice sheets formed, called glaciers, and moved southward to cover all of New England, even the highest mountains, and its outer limit was about where Long island is today. As the glaciers moved across Connecticut, they froze onto the loose, already eroded material and moved it forward, scraping the solid bedrock beneath it. These glacial grooves or striations are shown on the surficial maps of the Wallingford and Branford quadrangles. Some of the material scraped off the land surface by the glacial ice north of Connecticut was brought here by the moving ice and dumped. The general term for this type of land is glacial drift and, depending on how it was deposited, bears different names.(11)
The term “ice contact stratified drift” refers to materials deposited in the presence of ice and meltwater during deglaciation. It is usually sorted and includes sand, gravel, and small amounts of silt and clay arranged in layers by glacial meltwater. For the majority of its trip downhill to Long island Sound, the Muddy River runs through this type of material. The average depth of this stratified drift is 100 feet in thickness. Due to its porosity, stratified drift is the most productive type of aquifer. And, areas of stratified drift that are adjacent to streams, so that they are capable of quick recharge after use, are the most favorable areas for drilling wells. Plate A of the
Water Resources, Quinnipiac River Basin
U.S.G.S. publication, shows sites of wells drilled for the abovementioned reasons along the Muddy River. Also, note the surface water station at the Big Pine or Mackenzie Reservoir.(l2)
Till, a predominantly nonsorted sediment, consisting of boulders, gravel, sand, silt, and clay deposited directly by glacial ice, can be seen covering the majority of the Branford/Wallingford quadrangles. It averages about 25 feet in thickness. The amount of water available in all is relatively small. Due to its thinness of cover, wells drilled in till often run dry during summer months.(13)
The quality of ground water, as is the quality of surface water, is determined by the physical environment and the effects of man. A discussion of ground water quality in this part of Connecticut can be found in the
Water Resources, Quinnipiac River Basin
U.S.G.S. publication. In general, the quality of water is considered good, with caution in the areas of discharge of sewage, industrial and animal wastes, spreading of chemical fertilizers and road salt, solid waste disposal and intrusion of salty water in coastal aquifers due to overpumping of wells.(14)
