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Last modified
7/28/2009 2:42:09 PM
Creation date
4/30/2008 2:44:24 PM
Metadata
Fields
Template:
Weather Modification
Contract/Permit #
14-06-D-7052
Title
Ecological Impacts of Snowpack Augmentation in the San Juan Mountains, Colorado
Date
3/1/1976
State
CO
Weather Modification - Doc Type
Report
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<br />caveat acquires added importance from the fact that <br />large areas of wilderness ih the public lands are <br />managed with a preservation~st philosophy. Both <br />the Forest Service and the National Parks Service <br />require that proponents of weather modification <br />over wilderness areas provide assurance of no <br />impact. This may be interpreted as requiring proof <br />of a null hypothesis, not just its acceptance. <br /> <br />In predicting the effects 6f cloud seeding, the <br />danger of equating acceptance of H with proof of <br />H should be recognized explicitly? In speculating <br />agout the possible effects :of long-term winter <br />cloud seeding in the San J~n Mountains (Chapter II), <br />we have made an ad hoc att~mpt to define a median <br />position. Consequently, w~ have included in <br />Chapter II a discussion of ~ore effects than are <br />proven in the classical st~tistical sense by <br />rejection of H. Chapter II discusses effects that <br />are more likel? to occur t~an not, i.e. taking <br />p = 0.50 as the critical level. Using an inter- <br />mediate probability in this way offers a resolution <br />of the choice between producer's risk and consumer's <br />risk that is basic to many ;arguments about environ- <br />mental impact evaluations ~Pittock 1972). It allows <br />evaluations that are based :on ecological experience <br />as well as statistically s~pported decisions. <br /> <br />This approach also implies a need for periodic <br />evaluation of the predictions made in the light of <br />later knowledge, in the fa~hion that NEPA requires <br />in follow-up studies of impacts. There are obvious <br />costs incurred by speculat~on like that of Chapter <br />II, particularly in the increased risk of wrongly <br />predicting effects which dd not in fact occur. <br />Follow-up studies should be designed to detect such <br />erroneous predictions. <br /> <br />RESEARCH TACTICS <br /> <br />In this section, more specific topics of research <br />procedure are considered. These come from two <br />sources: they are either ~pproaches used or needs <br />defined by a number of subprojects in SJEP. The <br />more specific comments on procedure which apply <br />only to single studies are 'left for consideration <br />in the individual reports of Chapter IV. <br /> <br />Five topics are treated here: two involve climatic <br />influences on the ecosystem; one, the means of <br />manipulating these influences experimentally; and <br />the final two, the evaluation of responses in the <br />system. <br /> <br />Climatic Observations <br /> <br />r <br /> <br />In SJEP, the need to measu~e meteorological conditions <br />was met in a general way by maintaining weather <br />stations in the proximity of each study area. The <br />records from these central ,stations have been aug- <br />mented by more detailed observations on a micro- <br />scale within the study plots of greatest interest. <br />This procedure has overempqasized the importance of <br />the central weather station and we now recommend <br />that more attention be given to observations on <br />each study plot or sampled unit. <br /> <br />This recommendation results from the importance of <br />spring conditions to a study of snow ecology, and <br />the wide variability of en~ironmental conditions in <br />mountainous terrain at that time. Much of the work <br />reported in this volume sh~s the importance of snow- <br />melt conditions to plant gr'owth. During snowmelt, <br />steep environmental gradie~ts (e.g. in soil moisture <br /> <br />, <br /> <br />and temperature) are common, particularly in areas <br />close to the margins of melting snowdrifts. Thus, <br />local conditions cannot be easily estimated from <br />records of conditions only a few meters away, and it <br />would be better to maintain an observational record <br />for each study plot. These plot records may be of <br />lower precision than those from a central station <br />but this is offset by their more direct applicability <br />to the problems under study. <br /> <br />Many subprojects in SJEP have felt the need for more <br />information on snow conditions than has been avail- <br />able to them. Much of the information used in the <br />project has been collected haphazardly, rather than <br />as part of a coordinated program for snow survey. <br />For ecological work aimed at defining the importance <br />of snow, the depth (both total depth and water <br />equivalent) and duration of the snow cover should be <br />estimated for each detailed study plot. This is <br />particularly critical where wind drifting produces <br />a highly variable snowpack. Surveys of this sort <br />should also assist in defining the areas most likely <br />to trap the additional snow derived from cloud <br />seeding. <br /> <br />As a minimum, this work should define to within <br />a few days, the date of snow clearance on each study <br />plot. This date has obvious phenologic significance <br />and has been used extensively in SJEP as the best <br />single descriptor of snow conditions on each plot. <br />We recommend its continued use in studies of this <br />kind. <br /> <br />Snowpack Manipulation <br /> <br />In SJEP, a number of attempts have been made to <br />manage the natural snowpack on a local scale to <br />give experimental evaluations of the ecological <br />influence of the snow cover. Greatest success <br />derived from the use of snow fences in wind-swept <br />areas of the tundra. This experiment added signifi- <br />cantly to the natural snow accumulation on some <br />study plots; other plots were maintained as controls. <br />Similar experiments have been performed by adding <br />or by removing snow manually from experimental areas <br />to simulate differing snow conditions. No doubt <br />other means of snow manipulation for experimental <br />purposes can be found. The use of snow-making <br />machinery may be possible; irrigation may mimic <br />the effect of additional meltwater without a change <br />in the duration of the snow cover; shielding of the <br />ground surface by styrofoam may give the effect of <br />a longer duration without any change in the amount <br />of meltwater. <br /> <br />Experiments of this sort are recommended as a means <br />of evaluating snowpack-ecologic response relation- <br />ships. The aim of these procedures is not to <br />reproduce the actual effects of increased snowfall <br />which would probably not be distributed naturally <br />in a manner analogous to that in an experiment. <br />We have found no simple way of relating the local <br />effects of a snow fence to a generalIS percent <br />increase in snowfall but the experimental procedure <br />remains a most useful one in the study of ecologic <br />processes. <br /> <br />Evaluating Ecologic Responses <br /> <br />Two procedures have been found to have general <br />utility in evaluating ecologic responses to snowpack <br />augmentation changes in SJEP. The first of these <br />is a seasonal comparison of responses, and the second, <br />the selection of indicator species or situations <br />for study. <br /> <br />31 <br /> <br />., <br />
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