Hi All, I am working in i-Tree Hydro model which depicts the change in runoff due to change in tree and other land cover. After simulating the model, the results show that the Baseflow, pervious and impervious flows also have been reduced. Whereas, the baseflow should have been increased with a decrease in both other flows. The input parameters are percentage of tree, shrub, impervious and water cover and evergreen tree and shrub cover and the meteorological and evapotranspiration data. Please suggest some measures or change in percentage of parameters so as to get a higher baseflow.
Please share some more details. The model may require some tweaking.
Attached here is an output file for your reference. The model requires average annual flow, soil saturation conditions and type of soil, evaporation from ground and evapotranspiration, wind speed, dew point temperature, precipitation, land cover parameters including percentage of pervious and impervious area beneath the trees and percentage of directly connected impervious area to pervious area. The model depicts the change between base case and alternative case.
The land cover parameters in the file attached for your reference. The site is an urban area in Gurugram, India of 1.7 sqkm area. the site is approximately divided into half by two hydrological soil groups namely B and C. The soils are sandy loam and loamy sand.
I have not worked with i-Tree, but from the summary data you provided, the alternate case seems to have larger tree cover, which increases evapotranspiration from deeper soil layers. This might explain the lower total flow. I would check the evapotranspiration sums, if they are availalble somewhere, and perhaps try the computation with different tree cover values to see what is the effect of that parameter. Good luck with your modelling.
Hi,
You can add anthropogenic impacts, climate alteration impacts, urban and peri-urban developments
Understand the Hydrological cycle first. I think land use and topographic features are the important factors.
Try to get insight..
https://groups.google.com/forum/#!topic/swatuser/rBZZHOB7KvY
Considering that the soil profile, geology, topography, rainfall pattern in terms of intensity, distribution and duration, climatological parameters such as evaporation, transpiration, infiltration rate, etc, remaining constant over a period of time;, it is the effect of land use and land cover changes which alters the runoff pattern, Hence you may have to give more waitage to LULCC and other water usage parameters.
you write "Whereas, the baseflow should have been increased with a decrease in both other flows. " Is this based on actual observations or is it just your expectation based on the perceptive/conceptual model you have in mind?
Is it not that the your growing trees transpire more water compared with natural vegetation? That's why in South Africa, tree plantations have been declared streamflow reduction activities.
I-tree Hydro uses simple GIS function to calculate runoff and hydrological flows and still in development stage. So, any use of this for storm water should be with caution. Said that baseflow prediction from this software needs more careful evaluation. The connection from surface flows and baseflow is often through groundwater and subsurface flows. If the pervious cover is increased, it is expected to increase infiltration and ET and the influence on baseflow should be a net effect. I recommend calibrating the model well using local monitored data. Try to use other hydrological models like GWLF or SWMM to develop a more accurate hydrologic process in your watershed. Changing percent contribution to increase base flow may not be a good option given that baseflow component by itself is a complex process in watersheds. Hope this is helpful.
I could not understand the problem well. Real data shows an incease of baseflow but your model suggests decrease with baseflow?
if you mean base flow increases naturally, it shows an increasing in infiltration component of hydrologic water budget! or decreasing in ET and surface runoff. if you mean your model simulates over estimation of base flow it means rain loss parameters has not adjusted well.
In looking over the base and alternative, as suggested tree density is increasing and that means more transpiration in Texas pines likely. The number differences in connected imperveous surfaces and soil vs imperveous under canopy suggest also an increase in peakflow, reduction in baseflow. The value differences in this suggest a mistake perhaps as to why this changed so much. If you are just testing model with trial numbers, this can produce some unexpected results. I would review all the values related to imperveous. To have 65% imperveous under tree canopy seems unrealistic.
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