AS THE SNOW GOES A MULTIVARIABLE STUDY OF FACTORS THAT AFFECT LOSS OF SNOW. Erica David Pinedale High School, PO Box 279, Pinedale, WY 82941

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1 AS THE SNOW GOES A MULTIVARIABLE STUDY OF FACTORS THAT AFFECT LOSS OF SNOW Erica David Pinedale High School, PO Box, Pinedale, WY ABSTRACT: What are effects of environmental factors on sublimation of snow pack? There is a need to retain winter s snow pack to improve water supply during drought. Literature research provided information about sublimation, tree types, water supply, and snow pack variables. One intent of this project was to evaluate relationships of air temperature on tree branch resistance, because that affects unloading of intercepted snow from trees. A second intent was to evaluate effects of environmental factors on sublimation of snow. Procedures included two experiments. The first experiment used two conifer trees, a spring scale, and temperature probe to test flexibility of tree branches as temperature fluctuated over a -hour period. The second experiment tested effects of air temperature, relative humidity and wind speed on the mass of five ice and snow objects of varying shapes and densities over a -hour period. Two of the three branch resistance experiment hypotheses were supported. As temperature dropped, branches resistance to bending increased, and as temperature increased, branches resistance to bending decreased. Testing of Hypothesis of the branch bending experiment could not be finalized because temperature did not drop to a low enough level to find maximum resistance. All five of the sublimation experiment hypotheses were supported. As air temperature, wind speed, and object irregularity increased, sublimation increased. Also as relative humidity and object density decreased, sublimation increased. This current research can be used to emphasize the need to capture snow in dense, smooth snow pack wherever additional stored moisture will be needed in the spring. These results will help us improve our ability to retain as much snow for water supply as possible and more accurately predict probable spring water supply, as well as help us understand what is happening As the Goes! Keywords: intercepted snow, branch resistance, sublimation, snow pack, water supply. INTRODUCTION Much of the Western United States region is experiencing drought conditions. Residents are seeking ways to increase water availability from winter snowfall, rather than allowing this potential water supply to be lost (Figures and ). Figure. Western drought conditions. Figure. is a potential water supply. As the Goes is a study to investigate multiple factors that influence the loss of accumulated snow by sublimation. The goal is to use the results to decrease this loss of snow, which will then improve spring water supply. Interviews and literature research provided information about the processes of snow loss. Interviews with R.A. Schmidt and Robert Jairell (, personal communication) provided instruction about tree characteristics, branch interception, environmental conditions and sublimation, and suggestions for equipment and procedures. Schmidt (, ) and Schmidt and Gluns () had conducted extensive research on tree branch interception and loss of blowing snow, yet still suggested a need for additional work on effects of air temperature and conifer species on branch resistance to snow unloading. R.D. Tabler and his associates () researched blowing snow and sublimation extensively in their work for snow fence protection and water supplies. Tarboton () investigated factors of sublimation in a Utah field study with regard to measuring water for stream flow. The sublimation of ice objects had been investigated only for spherical ice objects and did not compare variables of shape and density. The first part of the investigation focused on resistance of conifer branches to bending. Trees intercept snow, which is quickly lost to sublimation if it is not unloaded onto the ground snow pack by the branches. The amount that a branch will bend affects the amount of snow it keeps on the branch

2 after interception during a snowstorm. The longer that the snow stays on the branch, the longer it is exposed to the environmental factors of sublimation. Warming periods allow branches to be more flexible, which causes them to unload their intercepted snow. Unloaded snow then becomes part of the denser snow pack retained on the ground, rather than being lost to sublimation. Dense, smooth snow pack is lost more slowly, providing better water storage, rather than allowing this potential spring water supply to sublimate. Sublimated snow is moisture lost back to the atmosphere rather than unloaded into the snowpack on the ground, where it can be retained longer. The first question was asked: Do changes in air temperature influence the conifer branches resistance to bending? Three hypotheses were stated:. As air temperature decreases toward freezing, resistance of the branch to bending will increase.. As temperature continues to drop below freezing, resistance of the branch will stabilize.. As temperature rises above freezing, resistance of the branch to bending will decrease. The second part of the investigation focused on effects of environmental factors on the sublimation of various shapes and densities of ice and snow objects. Sublimation is the change of a solid directly to a vapor, in this case the change of snow and ice directly to atmospheric water vapor. Scientists believe (R.A. Schmidt, personal communication) that there is actually a quasiliquid, half liquid, half solid, layer on the outer boundary of the snow or ice, which allows the water molecules to vaporize or sublimate (Figure ). As the environmental factors change, this layer could be affected. Further, as the shape or density of this surface layer changes, sublimation could change. The second question was asked: Do factors of air temperature, wind speed and relative humidity influence the sublimation of varying densities and shapes of snow and ice? Five hypotheses were stated:. As air temperature increases, sublimation will increase.. As relative humidity decreases, sublimation will increase.. As wind speed increases, sublimation will increase.. As density of the object decreases, sublimation will increase.. As irregularity of the object increases, sublimation will increase. These results will help us improve our ability to retain as much snow for water supply as possible and more accurately predict probable spring water supply, as well as help us understand what is happening As the Goes!. METHODS. Experiment Conifer Branch Resistance Test Area Set Up:. Select conifer trees, Lodgepole Pine (Pinus contorta) and Spruce (Picea spp.) (Figure ), each approximately meters tall, growing in similar soil moisture, and free of other obstructions.. On each tree, select branches that are meters long and do not interfere with other branches when pulled down cm. (Figure ).. Mark the pull point with flagging and a loop of string where the scale will be attached, cm in from the branch tip, to avoid over-flexible new growth or extremely rigid older growth (Figure ). Solid (snow) Sublimation Vapor Figure. Lodgepole and spruce used in testing. Quasi-liquid layer Figure. Sublimation solid vaporizes directly to a gas through the quasi-liquid layer. Figure. Measuring branch length and flagging pull point.

3 Data Collection:. Begin data collection during warmer part of day. Continue data collection for -hours. Test should cover both a warming and cooling period.. Use temperature probe to record ambient air temperature, and record whether tree is in shade, dark, or sun (Figure ).. Secure meter stick upright in snow, next to pull point of branch.. Secure spring scale hook to loop at pull point; use scale to gently pull branch down cm. (Figure ).. Measure the grams to flex branch, and calculate the Newton force of resistance.. Repeat step for three trials.. Repeat steps on each branch.. Repeat steps every hours for a -hour period. filled molds into clay base in freezer to keep stable until frozen (Figure ).. Remove ice cores from molds.. Gently pack snow around cores until they are approximately same dimensions and shape as ice counterparts, using small spheres to build snow spheres and tube shapes to build irregulars (Figure ). Figure. Freezing ice cores to pack snow around. Loose Objects Creation:. Find snow pack that is of low density, yet that is firm enough to carve a shape.. Carve spherical objects.. Use a needle and thread through a cm square paper base to create a loop to hold loose snow objects (Figure ). Figure. Probe to measure air temperature, and spring scale pulling down to measure branch resistance.. Experiment Sublimation of and Ice Ice Objects Creation:. Fill syringe with ml of water and empty into balloon; repeat for all balloons.. Insert both ends of a cm length of fishing line into balloon, making sure both ends are in the water.. Tie balloon with twist tie directly above water level and hang in freezer until frozen (Figure ). Figure. Carving snow for loose snow sphere. Test Area Setup:. Suspend -meter wire two meters above ground; designate separate areas to test wind and no wind.. For wind test area, set up two identical fans so that wind is blowing kph directly on one set of objects.. Hang two of each object (two each of ice spheres, ice irregulars, snow spheres, snow irregulars, loose snow spheres) in the wind area and two of each in the no wind area, cm apart from each other, secured with pin to avoid moving along line (Figure ). Figure. Freezing ice objects in balloons for ice sphere and ice irregular. Objects Creation:. Fill a cm diameter spherical mold with water; repeat times.. Insert both ends of a cm length of fishing line into mold, making sure both ends are in the water.. Fill a cm long hollow straw with water, seal one end with clay; repeat times.. Insert both ends of a cm length of fishing line into straw, making sure both ends are in the water; seal both ends of hollow tube with clay.. Set all water Figure. Setup of no wind and wind test areas with objects on line.

4 Data Collection:. Conduct tests when temperature is projected to stay below freezing for hours.. Record time, ambient temperature, ambient relative humidity, wind speed, and mass of each object.. Repeat step two every hours for hours (Figure ). Figure. Weighing object masses over -hour period.. DISCUSSION OF RESULTS. Summary of Results With regard to Question, Branch Resistance, two of the three hypotheses were supported, because as air temperature decreased, branch resistance increased, and as air temperature increased, branch resistance decreased. Hypothesis. could not be tested because air temperature did not drop low enough during the testing period. Graphs of these results are shown in Figures and. With regard to Question, Sublimation of and Ice, all five hypotheses were supported, because as air temperature, wind speed, and object irregularity increased, sublimation increased. Also, as relative humidity and object density decreased, sublimation increased. Results without wind are shown in Figures, and with wind are shown in Figures.. Discussion of Branch Resistance Results The -hour period began at : p.m. Data was taken every one to two hours during these hours. These hours were chosen so that a cooling and warming period would be investigated. Two species of tree were used, Lodgepole Pine (Pinus contorta) and Spruce (Picea spp). On each tree, three branches were tested. Branches were chosen so that each was of similar length and height above the ground, as well as being free from interference when pulled down cm, and representing three different sides of the tree. For consistency, each branch was pulled down three times per hourly test. The trees were located approximately meters apart. Air temperature around the trees varied due to sun and shade. As the shadow of a nearby building passed over the trees, the temperature changed, and affected the resistance of the branch. Other than the shade and sun, all the environmental conditions were similar for the two trees, such as soil moisture, wind exposure, and humidity. The lodgepole pine tree was. meters tall, with test branch lengths of.,., and. meters. The graph of the lodgepole results is shown in Figure. The temperature around the lodgepole pine ranged from a high of. C at : to a low of -. C at :. Over the -hour period the temperature decreased from -. C at : to the low of -. C at :, then increased to the high of. C at : the second day, and then ended with a decrease to. C at :. A matching pattern again was displayed in the resistance of the lodgepole pine branches. As the temperature dropped the branches resistance increased from an average of. N (Newtons) at : to an average of. N at :. The resistance then decreased to. N at :, in response to the temperature increase. The lodgepole pine branches pattern was similar to that of the spruce. The difference between the two trees was due to the spruce being in a more shaded area. Branch Resistance (N) : : Branch Resistance vs. Temperature - Lodgepole : : : : : : Time of Day : : : Figure. Lodgepole Branch Resistance : : Temperature (C) Branch Lodgepole Average (N) Branch Lodgepole Average (N) Branch Lodgepole Average (N) Lodgepole Average (N) Lodgepole Temp (C) The spruce tree was. meters tall, with test branch lengths of.,., and. meters. The graph of the spruce results is shown in Figure. The temperature around the spruce ranged from a high of -. C at : to a low of -. C at :. Over the -hour period the temperature decreased steadily from -. C at : to the low of -. C at :, then

5 increased to the high of -. C at : the second day, and then ended with a decrease to -. C at :. A matching pattern was displayed consistently in the resistance of all three spruce branches. As the temperature dropped the branches resistance increased from an average of. N at : to an average of. N at :, closely following the coldest temperature. Branch resistance then decreased to. N at :, responding to the temperature increase. The highest resistance matched the lowest temperature and the lowest resistance matched the highest temperature. Branch Resistance (N) : : : Branch Resistance vs. Temperature - Spruce : : : : : Time of Day : : : Figure. Spruce Branch Resistance : : Temperature (C) Branch Spruce Average (N) Branch Spruce Average (N) Branch Spruce Average (N) Spruce Average (N) Spruce Temp (C) In summary, there was a strong relationship between temperature and branch resistance. Hypothesis. was supported because as air temperature decreased to and below C the resistance of the branch to bending did increase. Hypothesis. was supported because as air temperature increased toward and above C the resistance of the branch to bending did decrease. Hypothesis. could not be tested, because air temperature did not fall low enough during the testing period. The changing of resistance could be due to freezing of the moisture within and between the cells, creating a stiffer and more resistant branch. The variation in resistance between the lodgepole and spruce could be due to differences in the species wood density and moisture retention. More resistant branches will retain more intercepted snow, and therefore expose more snow to sublimation, and loss of water supply for the spring. Recognition of each winter s temperature trends and warming and cooling patterns, along with the amount of snow intercepted by the dominant conifers, will allow scientists to predict more accurately the actual snow pack on the ground that will melt for spring water supply.. Discussion of Sublimation with No Wind Experiment Results The hours of this experiment began at pm. Data was taken every - hour during these hours. These hours were chosen so that a cooling and warming period would be investigated. The two trials of each variable were averaged for the following results. The air temperature and relative humidity measurements were the same for the Wind and No Wind parts of the experiment. During the first. hours (: pm to : am), air temperature was consistently low, ranging from C to C. humidity was consistently high, ranging from to %. From. hours to hours (: am to : pm), air temperature increased quickly during the morning to. C. humidity decreased suddenly to %. From to hours (: pm to : pm), air temperature dropped back to. C and relative humidity increased back to %. Each object was exposed to these similar conditions, one set in no wind and a second set in a wind of kph. The Control, a No Wind Ice Sphere (Figure ), increased its mass. g, from an initial. g to. g, during the first. hours when air temperature was consistently low and relative humidity was consistently high. From. hours to hours, as air temperature increased and relative humidity decreased, the No Wind Ice Sphere decreased in mass. g, from. g to. g. From to hours, air temperature began to drop, relative humidity began to increase, and the No Wind Ice Sphere stopped decreasing in mass, maintaining at. g for the final hours. Net mass lost was. g. This data pattern supports Hypothesis. and., as air temperature increases and relative humidity decreases, sublimation increases.

6 Temperature (C) - - Control: No Wind Ice Sphere Mass Change Over Time Figure. Control No Wind Ice Sphere Object Control: Ice Sphere Control: Ice Sphere The second No Wind object changed the variable of shape from the Control s sphere, to a longer, thinner, irregular shape with more surface area to represent intercepted snow lying on tree branches. The No Wind Ice Irregular (Figure ) increased its mass. g, from an initial. g to. g, during the first. hours when air temperature was consistently low and relative humidity was consistently high. From. hours to hours, as air temperature increased and relative humidity decreased, the No Wind Ice Irregular decreased in mass. g, from. g to. g. From to hours, air temperature began to drop, relative humidity began to increase, and the No Wind Ice Irregular slowed its decrease in mass, dropping only. g, down to. g during the last hours. Net mass lost was. g. This data supports Hypothesis., as the irregularity and surface area of the object increases, sublimation increases. Temperature (C) - - No Wind Ice Irregular Mass Change Over Time Object Ice Irregular Ice Irregular from an initial. g to. g, during the first. hours, when air temperature was consistently low and relative humidity was consistently high. From. hours to hours, as air temperature increased and relative humidity decreased, the No Wind Sphere decreased in mass. g, from. g to. g. From to hours, air temperature began to drop, relative humidity began to increase, and the No Wind sphere slowed its decrease in mass, dropping only. g, down to. g during the last hours. Net mass lost was. g. This data supports Hypothesis., as the density of the object decreases, sublimation increases. Temperature (C) - - No Wind Sphere Mass Change Over Time Figure. No Wind Sphere Object Sphere Sphere The fourth object, the No Wind Irregular, allowed comparison of both the shape and density. The No Wind Irregular (Figure ), increased its mass. g, from an initial. g to. g, during the first. hours, when air temperature was consistently low and relative humidity was consistently high. From. hours to hours, as air temperature increased and relative humidity decreased, the No Wind Irregular decreased in mass. g, from. g to. g. From to hours, air temperature, slowed its decrease in mass, dropping only. g, down to. g during the last hours. Net mass lost was. g. This data further support Hypotheses. and., as density decreases and irregularity and surface area increases, sublimation increases. Figure. No Wind Ice Irregular The third object changed the variable of density of material from the Control s spherical ice to spherical packed snow. The No Wind Sphere (Figure ), increased its mass. g,

7 Temperature (C) - - No Wind Irregular Mass Change Over Time Figure. No Wind Irregular Object Irregular Irregular The fifth object, the No Wind Loose Sphere, allowed further comparison of density. The No Wind Loose Sphere (Figure ) was placed into the experiment at hour.. It was not placed earlier because the snow conditions did not allow carving of loose snow into a spherical shape. From. hours to hours, as air temperature increased and relative humidity decreased, the No Wind Loose Sphere decreased steadily and rapidly in mass, losing. g, from. g to. g. Net mass lost was. g, well over % of its initial mass. This data further support Hypothesis., as density decreases, sublimation increases. Temperature (C) - - No Wind Loose Mass Change Over Time Object Loose Sphere Loose Sphere Figure. No Wind Loose In summary, in the No Wind Objects, there was a definite relationship between shape, surface area, density, and sublimation (Figure ). All the less dense objects had more sublimation, both in amount and rate, than the denser Ice objects. Also, all the Irregular objects with more surface area, had more sublimation, both in amount and rate, than the Spherical objects. This points to a conclusion that lower density, more irregularity and more surface area all contribute to an increase in sublimation amount and rate. Not only did object characteristics contribute to sublimation differences, but the environmental factors of relative humidity and ambient air temperature also played a key role. Consistently, as humidity dropped and temperature rose, sublimation rate increased. Temperature (C) - - All No Wind Objects Average Mass Figure. All No Wind Objects Object Humidity (%) Air Temp (C) Control: Ice Sphere Ice Irregular Sphere Irregular Loose Sphere. Discussion of Sublimation with Wind Experiment Results: The next set of objects, the Wind Objects, were hung in a kph fan-powered wind during the same -hour period, so air temperature and relative humidity patterns were identical to the previous description. The Wind objects data were compared to those in No Wind and to each other. The first object, the Wind Ice Sphere (Figure ), increased its mass. g, from an initial. g to. g, during the first. hours when air temperature was consistently low and relative humidity was consistently high. From. hours to hours, as air temperature increased and relative humidity decreased, the Wind Ice Sphere decreased steadily in mass,. g, from. g to. g. Net mass lost was. g. compared to a. g for the Control No Wind Ice Sphere. This supports Hypothesis., as wind speed increases, sublimation increases.

8 Temperature (C) Humidity(%) - - Wind Ice Sphere Mass Change Over Time Figure. Wind Ice Sphere Object Ice Sphere Ice Sphere The second Wind object changed the variable of shape from the Control s spherical to a longer, thinner, more irregular shape. The Wind Ice Irregular (Figure ) increased its mass. g, from an initial. g to. g, during the first. hours when air temperature was consistently low and relative humidity was consistently high. From. hours to hours, as air temperature increased and relative humidity decreased, the Wind Ice Irregular decreased steadily in mass. g, from. g to. g. Net mass lost was. g., compared to. g loss with No Wind Ice Irregular. This supports Hypothesis., as wind speed increases, sublimation increases, and Hypothesis., as irregularity of the object increases, sublimation increases. Temperature (C) - - Wind Ice Irregular Mass Change Over Time Time From Start Object Ice Irregular Ice Irregular and relative humidity was consistently high. From. hours to hours, as air temperature increased and relative humidity decreased, the Wind Sphere decreased in mass. g, from. g to. g. Net mass lost was. g, compared to. g. for the No Wind Sphere and. for Wind Ice Sphere. This supports Hypothesis., as wind speed increases, sublimation increases, and Hypothesis., as density of the object decreases, sublimation increases. Tempurature (C) - - Wind Sphere Mass Change Over Time Figure. Wind Sphere Object Sphere Sphere The fourth Wind object, the Wind Irregular, allowed comparison of shape, density, and wind. The Wind Irregular (Figure ) increased its mass. g, from an initial. g to. g, during the first. hours, when air temperature was consistently low and relative humidity was consistently high. From. hours to hours, as air temperature increased and relative humidity decreased, the Wind Irregular decreased steadily in mass. g, from. g to. g. Net mass lost was. g, compared to. g for the No Wind Irregular. This supports Hypothesis., as wind speed increases, sublimation increases, and Hypothesis. and., as density of the object decreases and irregularity increases, sublimation increases. Figure. Wind Ice Irregular The third Wind object changed the variable of density of material from the Control s spherical ice to spherical packed snow. The Wind Sphere (Figure ) increased its mass. g, from an initial. g to. g, during the first. hours, when air temperature was consistently low

9 Tempureature (C) - - Wind Irregular Mass Change Over Time Figure. Wind Irregular Object Irregular Irregular The fifth Wind object, the Wind Loose Sphere, allowed further comparison of density and wind effects. The Loose Spheres (Figure ) were placed into the wind experiment at. hours and fell off the strings at. hours. From. hours to. hours, as air temperature increased and relative humidity decreased, the Wind Loose Sphere decreased steadily and rapidly in mass, losing. g, from. g to. g. over a -hour period. Net mass lost was. g, well over % of its initial mass. This data further support Hypothesis., as wind speed increases, sublimation increases, and Hypothesis., as density decreases, sublimation increases. Tempurature (C) - - Wind Loose Mass Change Over Time Figure. Wind Loose Object Humidity (%) Air Temp (C) Loose Sphere Loose Sphere In summary, in the Wind Experiment set, there was still a definite relationship between shape, surface area, density, and sublimation (Figure ). All the objects had more sublimation, both in amount and rate, than the Ice objects. Also, all the Irregular objects had more sublimation, both in amount and rate, than the Spherical objects. Further, all the Wind experiment objects had more sublimation than their counterparts in No Wind experiment. Temperature (C) - - All Wind Objects Average Mass Figure. Wind All Objects. CONCLUSION Object Humidity (%) Air Temp (C) Ice Sphere Ice Irregular Sphere Irregular Loose Sphere This research project focused on understanding factors that affect the loss of snow in order to potentially predict water availability. Two of the three branch resistance experiment hypotheses were supported. As temperature dropped, branches resistance to bending increased, and as temperature increased, branches resistance to bending decreased. Hypothesis of the branch bending experiment could not be tested because air temperature did not drop to a low enough level. All five of the sublimation experiment hypotheses were supported. As air temperature, wind speed, and object irregularity increased, sublimation increased. Also as relative humidity and object density decreased, sublimation increased. These results can be used to emphasize the need to capture snow in a dense, smooth snow pack to store moisture and avoid loss by sublimation. Closer estimations of spring water supply can be made based on temperature, humidity and wind patterns throughout the winter. These results will help us improve our ability to retain as much snow for water supply as possible and more accurately predict probable spring water supply, as well as help us understand what is happening As the Goes!. IMPROVEMENTS AND EXTENSIONS The results could have been affected by several factors that could be improved in future research. Light As the -hour experiment period progressed, light could have been an influential variable. This could be improved by including

10 another set of objects in an area where the lighting was controlled. Boundary Layer Measurements The temperature and humidity probe measured the ambient conditions, but did not measure right at the boundary layer of the air and ice/snow objects. This made it difficult to determine if there was an actual temperature and humidity difference between the wind and no wind objects. High Temperature During the branch bending experiment, the temperature did not fall to low enough levels to test branches in extreme cold temperature ranges. This could be improved by testing during a colder period. Extensions to the branch resistance experiment could include the moisture content of the branches, to project the branch resistance in trees being affected by drought, as well as interception by sagebrush, since much of the drought afflicted area is covered in sage (Figure ). To extend the sublimation experiments, research could next include effects of daylight versus dark, and sublimation of the ground layer snow, since not all snow is intercepted (Figure ). Another extension could evaluate the airflow patterns and vortices at the boundary of the ice and snow objects quasi-liquid layer and the ambient air during the sublimation process to more fully understand the function of the wind on snow on the ground and that intercepted by branches (Figure ).. ACKNOWLEDGEMENTS First, I d like to acknowledge R.A. Schmidt and Bob Jairell, hydrologists, who have helped me for many hours in person and over the phone. They guided me on scientific concepts and introduced me to previous research about loss of snow, branch resistance, and sublimation. Most importantly, they have been friendly and encouraging so that I became comfortable talking with experienced, professional scientists, about my own projects. Second, I d like to thank my grandparents who allowed me to use their trees and house overnights for branch resistance experiments, and my family, who helped me gather equipment for both of the experiments and drove me to meet with R.A. Schmidt and Bob Jairell.. REFERENCES Daffern, T., : Avalanche Safety for Skiers and Climbers. Mountaineers, pp. Schmidt, R.A., : Sublimation of Wind- Transported A Model. Rocky Mountain Forest and Range Experiment Station. Schmidt, R.A., : Sublimation of Intercepted by an Artificial Conifer. Rocky Mountain Forest and Range Experiment Station. Schmidt, R.A. and D.R. Gluns, : fall Interception on Branches of Three Conifer Species. Canadian Journal of Forestry Res.,, -. Tabler, R. D. : Design Guidelines for the Control of Blowing and Drifting. Tabler & Associates, pp. Figure. also is intercepted by sagebrush and falls through to the ground without interception. Tarboton, D., : Measurement and Modeling of Energy Balance and Sublimation from. Proceedings, International Science Workshop, bird, UT, Utah Water Research Laboratory working paper #WP--HWR- DGT/. Figure. Potential water supply in intercepted snow.