Continued monitoring of water quality in restored Doan Creek
I have spent my semester of internship work testing water at six locations in and around Doan Creek at the Whitman Mission National Historic Site. My internship project is a continuation of the volunteer work that I completed last semester for Whitman’s environmental internship course. I originally chose to work with Roger Trick at the Whitman Mission to monitor the chemical conditions of the restored creek because of the connections of this project to my field of study, chemistry, and to my interest in watershed restoration.
Because I had greatly enjoyed my work, I decided to continue with sampling the water for another semester. I believe that continually collected data is invaluable for accurately determining whether or not the new portion of Doan Creek will be able to sustain wildlife in the future. Roger and I were only able to collect 4 complete sets of data on the water prior to this term and I had hoped to build a table spanning as near to a full year as possible. Having an year’s worth of data would allow easy comparison of over time and demonstrate the effect of seasonal changes in the tested parameters.
Doan Creek, the newly restored stream, runs through the grounds of the Whitman Mission. For over 70 years, the creek’s course has been routed for irrigation purposes and, therefore, has not been a suitable habitat for fish. Last year, a project was approved to be implemented this fall that would restore Doan Creek to its original path. The addition would connect Doan Creek to Mill Creek and provide for future fish passage. Although the digging of this new portion was completed last semester and some testing was performed in it, the creek bed was dry for the majority of this semester. Recently water began to slowly flow into the creek and volunteers added riffles and pools to the bed. With further plans for controlling non-native plants, such as canary grass, and continued planting of native vegetation, the creek restoration is expected to be fully completed by the spring of 2006 or the fall of 2007. Because there was not water to test in the restored portion of the creek, I only obtained data for the last three weeks of this semester’s collection which made comparisons to last semester’s data difficult.
The parameters which have been monitored are pH, dissolved oxygen, turbidity, and temperature at 6 different locations including the Creek, the irrigation ditch, and Mill Pond. These locations should provide a good idea of quality of the water in the new Doan Creek portion once the restoration is complete. According to the Environmental Protection Agency (EPA) in their recommended elements of a state monitoring system, these characteristics are appropriate to be tested in order to determine the feasibility of the stream as a habitat for fish. This semester, I have continued my work by testing in the same manner as before, using a portable microprocessor turbidity meter and a dissolved oxygen meter which also detects temperature along with colorpHast pH strips.
I found last semester that all of the water tested, with the exception of Mill Pond, was well within the desired values for salmon and trout rearing and migration as outlined in the Washington State Department of Ecology’s water quality standards. The newly collected data for the year also falls within these parameters. With my extended range of data, I was able to make comparisons to observe the seasonal effect upon each of the testing conditions. Although some of the data variation could be the result of inaccuracy of the instruments and testing methods used, the data seemed consistent during the testing period giving me more confidence in it. To observe seasonal changes, I averaged each parameter for the sites in the original Doan Creek, the irrigation ditch, Mill Pond, and the restored Doan Creek according to time periods of similar temperature. From this data, the dissolved oxygen appears to have increased over the span of time from fall to spring, but the change is slight. From my knowledge of stream water quality, I would have expected the dissolved oxygen to change because of increased levels of both photosynthesis and decomposition in warm weather. The small increase is probably due to these factors as warmer water is usually able to hold less dissolved gas. The turbidity in the stream shows increases in all locations with the changing seasons. I would attribute this increase to the observed decrease in water flow with the cold season and then to the withdrawal of water for summer irrigation. The third tested parameter, pH, did not vary much between seasons which would be expected. If the current conditions of Doan Creek and the irrigation ditch are valid indicators of the future of the new portion of Doan Creek, I would anticipate for it to be a healthy stream, able to successfully sustaining fish, such as salmon and trout, and other wildlife.
In addition to analyzing the collected data for seasonal changes, Roger asked me to consider which testing sites could be eliminating in future water tests. Next year and over the summer, there may not be a volunteer focusing their time upon water quality testing as I have been doing over the past months. In order to make the process more efficient for the park service, I determined two testing sites that could be eliminated. The dissolved oxygen data for all of the sites except for the Mill Pond was analyzed using the Bonferroni correction in the statistical analysis program Minitab, but no significant variance was shown. I analyzed the turbidity data in a similar manner using the Tamhane correction and significant variance was shown between all of the sites except for 1 and 4 and 6 and 7. According to this analysis, the data for sites 1 and 4 and for sites 6 and 7 were similar enough for only one of each to be tested in the future. Due to their physical locations, I would suggest that sites 4 and 6 be dropped. Roger also said that he plans to focus the testing on sites closer to and in the restored creek once water is allowed to flow through it. I would also recommend that the testing procedure be continued in a manner very similar to my own in order to ensure consistency in the readings and to minimize error.
Overall, I have had a wonderful time assessing the water quality of Doan Creek during the past year. Roger, especially, and the other employees at the Whitman Mission were constantly accommodating. It has been an interesting experience to learn about the responsibilities of the National Park Service and the ways in which the parks work together to accomplish their goals. The most exciting part of my internship has been watching the rapid progress of the restoration project which has gone from flat land to a creek bed, complete with riffles and pools in fewer than 8 months. From the indications of my data, I will someday return to find Doan Creek thriving with plants and wildlife.
Whitman Mission Historic Site
328 Whitman Mission Road
Walla Walla, WA 99362