Elm Fork Trinity Watershed

Transcription

1 Elm Fork Trinity Watershed Environmental Science Lab Sam Negus Rachel Smartt Jessica Rodriquez Clarissa Hodges Lindsay Patterson

2 Elm Fork Trinity Watershed The Trinity River is a major water supply for Texas. This river is 710 miles long with four branches. For this particular field study we concentrated on the Elm Fork section which comes from Gainesville to Denton. The water coming from the Trinity River is important because it is a source of drinking water for homes and businesses in the North Texas area. It is important to perform field tests in order to make observations and collect data. Specifically concerning the field study we just conducted you want to know that the area in which you are getting drinking water is clean and healthy but this cannot be done by just eyeballing the land and water. We were able to get actively involved in the process by performing six assessments in order to obtain the answer of the health and cleanliness of the Elm Fork Trinity Watershed. The six tests were soil analysis, soil infiltration, water quality analysis, habitat assessment, stream velocity and discharge, and biomonitors. While performing all these tasks we were able to fully appreciate the environment and the processes that make it work. The stream velocity is the speed of the water in the stream. The stream velocity is greatest in midstream near the surface and is slowest along the stream bed and banks due to friction (Stream Solute Workshop, 1990). According to the Elm Fork Trinity Watershed Field Study Data, the average stream velocity of the Elm Fork Trinity River is 0.94 m/sec. The data was gathered by dividing the distance traveled (10m) by the average time (10.61s). Water flowing through a stream performs three kinds of geologic work. Moving water erodes material from the bed and sides of the channel, transports the eroded material to a new location, and then deposits it. The ability of a stream to do work is a function of stream velocity and discharge.

3 A stream discharge is a measurement of how much water flows through a stream in one second. This measurement is calculated using measurements of stream width, depth, and velocity. The following equation defines stream discharge mathematically: Q = V x W x D. Where Q is the discharge, V is the velocity, W is the average width and D is the average depth of the flow (Stream Solute Workshop, 1990).It is measured in cubic meters per second. Stream discharge varies over both time and space. Discharge normally increases downstream as more water enters the stream channel from runoff and groundwater flow. According to the Elm Fork Trinity Watershed Field Study Data, the total stream discharge of the Elm Fork Trinity River is 7.84 m3/ sec. The total stream discharge was gathered by multiplying the total stream cross- section area (8.34 m 2) by the average stream velocity (0.94m/sec). Discharge varies temporally because of chaotic behavior of its inputs, such as precipitation or melting snow. As discharge increases, corresponding changes in velocity, channel depth and width are made within the stream system. Of the three variables that change within the stream system with an increase in discharge, velocity is the least responsive (Stream Solute Workshop, 1990). While conducting a field study at the Elm Fork Trinity Watershed, we were able to identify three different types of soil. They are loam sand, sandy loam, and sandy clay. Soil is important to the health of the watershed because it s a place where atmosphere, water, sun, and organisms interact in order to support life. During the soil analysis we looked at the soil color, structure, texture, ph, and qualitative measurements of nutrient levels taken from the soil samples. Overall the soil is good quality, it contains a mixture of clay, sand and other organic matter. Good quality means that the soil will not be easily compacted, has good drainage, thus making it pretty fertile. The nutrient levels in the soil are inversely tied to the ph levels.

4 Nitrogen, phosphorus, and potassium are all nutrients that make sure that plants are able to grow and flourish. It also enables them to be able to fight off bacteria and other diseases. The primary nutrient that was present was potassium. This nutrient also happens to be the key essential ingredient for plant growth. After putting all this data together we were able to go onto the second part which involves the soil infiltration rate. The information collected was looked at over a period of 45 minutes (Figure 1). During the first minute of infiltration the infiltration rate was high at 12 mm. In the next minute it went down to 2mm. This says that the soil was dry which is why the first number was so high. Infiltration rate is influenced by the soil structure, texture, and soil type. Based on the information that we collected I was not surprised to discover that the soil was as dry as it was. That could be due to factors such as lack of rainfall, the ph balance of the soil which was a little high at 7 and 8, and the little amount of nitrogen and phosphorous present in the soil. Overall the soil has fairly good quality but could be healthier.

5 Figure 1 Based on the results of the field study data sheet there is a considerable amount of different species types within the Elm Fork Trinity Watershed. Being that stoneflies are extremely territorial, there is evidence to support that mayflies have been affected by their increase in population (Peckarsky, 1980). Among the insect invertebrates there were found five stoneflies (Plecoptera), one true bug (Hemiptera), four hellgrammites (Megaloptera), two water beetles (Coleoptera), thirteen caddis flies (Trichoptera) and sixteen true flies (Diptera). Among earthworms (Oligochaeta), of which had the highest population count within the species found. Birds rely on the availability of insect invertebrates to strengthen their breeding cycle. Based on the evidence that there is plentiful insect invertebrate present in the Elm Fork Trinity Watershed, it is determined that other non-aquatic life are able to live and flourish throughout the

6 test area (Krapu, 1974). The overall quality of the water resulted in on the Index of Biotic Integrity, rating the quality good. There are plenty of species present to categorize this watershed as a clean and healthy watershed. Although there was a decreased number of insect invertebrates in some species categories, the final result were fair for a safe and healthy environment. In Elm Fork Trinity Watershed out by Lake Lewisville we did tests to find out the different levels of chemicals, dissolved oxygen, and the ph in the water (Table 1). We tested different parts of the water, some with different temperatures. Starting with Reach A Site 1 it had a temperature of 25 degrees Celsius, a ph level of 7, and a dissolved oxygen level of the 7 mg/l. Also we checked for turbidity, that is the cloudiness of the water. This could affect the disinfection of the water, so this process is important. Reach A Site 1 had an average of 42 cm. On Reach A Site 2, the temperature was 26 degrees Celsius, the dissolved oxygen level was 9mg/L, and the ph level 8. The Turbidity for this site was an average of 42.7 cm. Last was Reach A Site 3 which has a temperature of 25 degrees Celsius, ph level of 8, and a dissolved oxygen level of 8mg/L. Site 3 had a Turbidity average of 45.3 cm. Qualitative Summary of Basic Water Quality Parameters Parameter Tested Reach A Site 1 Reach A Site 2 Reach A Site 3 Ammonia Negative Negative Negative Chlorine Negative Negative Negative Chromium Negative Negative Negative Copper Negative Negative Negative Cyanide Negative Negative Negative Iron Negative Negative Negative Nitrate Negative Negative Negative

7 Parameter Tested Reach A Site 1 Reach A Site 2 Reach A Site 3 Phosphorus Positive Positive Positive Silica Positive Positive Positive Sulfide Negative Negative Negative Table 1 The Elm Fork Trinity Watershed rated high for aquatic life based on the habitat quality. Several visual tests were conducted such as bank stability, channel flow and the dimensions of the largest pool. Each of the nine test were rated on a three-point or four-point scale (Figure 2 and 3). Each of the individual scores were added together, giving the area a total score of 21, of a possible 31 points. The Elm Fork Trinity Watershed rated a top score on bottom substrate stability and bank stability. The results imply in the watershed had 50% or more gravel in the bottom substrate and had less than 10% evidence of erosion or bank failure. Where the watershed scored lowest was in the dimensions of the largest water pool. No existing pools were visible, only shallow pockets. The additional tests, available in-stream cover for aquatic life, the number of riffles, channel water flow, channel sinuosity, riparian buffer vegetation and the aesthetics of the reach scored in the middle range.

8 Figure 2 Figure 3 As stated before, the Trinity River is a major water source for many species. Many important factors can be learned from this study. The six tests conducted in this study are able to provide information on the human drinking water supply, the water quality for aquatic life and the general aesthetics of the river. All three elements are important indicators of the surrounding environment. For example, any fluctuation in soil nutrients or ph levels may provide imperative information as to point and non-point source pollutants in the surrounding areas which may adversely affect plant and animal life. Obviously, our class was not able to participate in the

9 analysis of the Elm Fork Trinity Watershed. Therefore, it is difficult to determine what elements may have been improved upon. References Krapu, G. L Feeding ecology of pintail hens during reproduction. The Auk, 91.2 : Peckarsky, B. L. Predator-prey interactions between stoneflies and mayflies: behavioral observations. Ecological Society of America, 61.4 : Stream Solute Workshop Concepts and Methods for Assessing Solute Dynamics in Stream Ecosystems. Journal of the North American Benthological Society. 9 :