Watershed Experiments
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Transcript of Watershed Experiments
![Page 1: Watershed Experiments](https://reader036.fdocuments.in/reader036/viewer/2022083004/56812f34550346895d94c669/html5/thumbnails/1.jpg)
Watershed Experiments
Lab 3
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Watersheds• Several different designs
– Single watershed (data for modeling)– Nested (evaluate accumulated effects)– Paired (cause and effect)
• Watershed studies were important for detection of environmental problems such as acid rain and climate change.
• Very Expensive and difficult to do process research• Look at long-term trends, cumulative-impacts, and develop models
with data.• Most of our knowledge on the impact of land use on watershed
scale processes are from paired watersheds. Processes include:– Runoff volume (water yield)– Peak Flows (flooding)– Sediment Yield – Other water quality parameters (N, P, K, etc.)
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Watersheds
• Nested Design
• Can Evaluate:– Scale effects
– Hillslope to channel
– Spatial processes
– Cumulative impacts
Walnut Gulch Experiment Watershed
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Paired Watershed • Watersheds should be similar
(geology, soils, terrain, vegetation, etc.)
• Need to develop a relationship between watersheds before treatment (i.e pre-treatment)
• You need to collect data for years before the treatment is implemented.
• This is an experiment in an uncontrolled environment.
• Potential disturbance can disrupt the experiment.
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H.J. Andrews Experimental ForestOregon, USA
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Paired Watersheds
• Multi-factorial experiment is where more then one factor varies over time.
• To understand the relationship between response and treatment we must take measures over different levels of all the factors. In our case we are looking at response over a series (i.e. years) of environment conditions (e.g. climate).
• Develop relationships for two time periods, pre-treatment and post-treatment. Test to see if they are statistically difference.
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Statistical Test• We will develop two regression model for pre- and post-treatment time
periods where:
– SFF-pre = a1 + b1 * SFD-pre
– SFF-post = a2 + b2 * SFD-post
• SF = Annual Streamflow (inches) • F = Watershed F• D = Watershed D
• We will test to see in the equation coefficients are equal where the HO: a1=a2 and b1=b2.
• If one of the tests is rejected the equations are not equal which indicates we may have a treatment effect.
• Watershed D is the Control watershed and Watershed F is the Treated watershed. Watershed F was treated with herbicides to kill deep-rooted shrubs and was converted to grass.
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Statistical Tests
Watershed D Watershed D
Watershed F
b1≠ b2 a1 ≠ a2
Pre
Post
Pre
Post
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Water Yield Increase
• If there is a treatment effect that the Increase in water yield can be computed as:– WYI = SFf-post – [a1+b1*SFd-post]