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Project Completion Report / OWRT Project No. A-027-ARIZ / Development of a mathematical model of infiltration which includes the effects of raindrop impact / Agreement No. 14-31-0001-3503 / Project Dates: July 1971-December 1972. / The purpose of this investigation was to use an existing mathematical model of infiltration to assist in determining which factors, including raindrop impaction, were responsible for infiltration characteristics of a bare semiarid watershed. The infiltration model developed by Roger Smith was selected as best suited for this investigation. Several laboratory and field rainfall simulator runs were modeled. Good correlation was found between the modeled and experimental results for both the infiltration data and the saturation profiles, for both bare and grass covered plots. For the lab and field experiments a realistic rotating disk rainfall simulator was used. In the field tests bare and grass covered plots were tested. In the lab specially constructed soil boxes were used that permitted measurement of infiltration and saturation profiles with time. Gross changes in saturated hydraulic conductivities due to crusting effects were also measured. Gamma ray attenuation techniques were used to obtain density and soil moisture profiles for the laboratory experiments. It was found that the Smith model can be used to simulate infiltration from different surface conditions as long as there is some method to calibrate the model. Carefully obtained saturated and unsaturated hydraulic properties for the soil types present in the watershed are needed in addition to infiltration data from a realistic rainfall simulator or through hydrograph analysis from unit subwatersheds.

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A case study of dry well recharge / Research Project Technical Completion Report (A-114-ARIZ) / Prepared for the U.S. Department of Interior / September 1983.

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Stormwater is the component of runoff that is generated by human activities, and has gradually become a key issue in achieving sustainability in urban environments. When vegetation and soils are replaced with roads and buildings, less rainwater infiltrates into the ground or is taken up by vegetation, and more becomes surface runoff. A greater area of impervious surfaces leads to increased stormwater runoff volume and velocity, and consequently increases the risk off looding and erosion. Being able to reduce stream flows and pollution of surface flows, green roofs are one technology that may help in alleviating this storm water crisis. This thesis developed a different and effective methodology for quantifying the effects of green roofs on stormwater runoff and calculating the runoff volume and rate for residential housing communities before and after applying green roofs. The method utilizes local climate data like rainfall and evapotranspiration rate, the water use properties of vegetation like crop coefficients of plants, and the areas of impervious surfaces; and then compares the different effects of green roofs in different locations having disparate climatic conditions. It was found that the best way to achieve zero runoff was to green a portion of the total rooftop area and disconnect all impervious surfaces. Implications of this methodology on city planning and site design and for future research are then discussed.

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The Canagagigue Creek watershed, located in the Grand River Basin, is one of the fastest developing areas in Ontario. The watershed hydrology has changed considerably due to the increased anthropogenic activities, producing frequent floods and droughts as well as water quality problems. MIKE SHE, a watershed-scale model, was used to simulate surface runoff from the Canagagigue Creek watershed. Various management scenarios affecting the surface hydrology were also evaluated. The model was calibrated for four years (1994-95 to 1997-98) and validated for another four years (1990-91 to 19931-94). For the calibration period, the correlation between the observed and simulated daily runoff was satisfactory, as shown by the coefficient of determination value of 0.59. The coefficient of determination was 0.44 for the validation period. The Nash-Sutcliffe coefficients obtained were 59% and 40% for the calibration and validation period, respectively. Use of daily input data together with a simplistic snowmelt routine, was found to affect model performance during the winter/spring period. Henceforth, model performance can be greatly improved by adopting a more comprehensive method for simulating snowmelt and incorporating the frozen soil conditions. Overall, the model was able to simulate surface runoff reasonably well on annual, seasonal, monthly, and daily intervals, representing all the hydrological components adequately. / With the various management scenarios simulated, it was found that the deforestation scenario considerably increased the total flow (11%). On the other hand, the high runoff peaks were decreased and low flows were increased considerably in the application of the tile drainage scenario. It was also observed that surface flow increased in wet years and decreased in normal and dry years in the climate change scenario. Though impacts of certain scenarios were almost negligible, their effects were significant when associated with the percentage area under transformation. Hence, it was concluded that the model can be used to simulate various management scenarios to solve hydrologic problems in the Southern Ontario climatic condition.

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