The increasing availability of web mapping tools creates new opportunities to bridge decision-makers' climate information needs with technical capabilities. These new tools, however, raise familiar, unresolved issues related to cartographic representation. Using an on-line drought mapping tool, this study seeks to understand which spatial unit best meets the desire drought managers have for ‘‘local'' information, their comprehension of uncertainties introduced in mapping information at local scales, and their willingness to trade off accuracy for information at a desired unit. We found that the most useful local map information includes regional context and boundaries which present their local area of interest. Even among this experienced, well-educated, professional group, those who had not taken a GIS or cartography class did not fully recognize the role of interpolation in creating and introducing uncertainty to some drought maps. Those who did recognize the uncertainty introduced by interpolation still strongly favored maps that provided estimated values for all areas vs. station point accuracy. Mapping poses a unique set of challenges to communicating risk and uncertainty. As more decision-support efforts incorporate web mapping, greater attention is needed to assure that users understand the tradeoffs between accuracy and precision in creating local information, the imprecision of boundaries, as well as the limits of forecasts. Clearly conveying spatial accuracy and uncertainty is a challenge that merits greater attention in using maps to communicate drought and other environmental risk information.
Tree rings offer a means to extend observational records of streamflow by hundreds of years, but dendrohydrological techniques are not regularly applied to small tributary and headwaters gages. Here we explore the potential for extending three such gage records on small streams in the Wind River drainage of central Wyoming, United States. Using core samples taken from Douglas fir (Pseudotsuga menziesii), pin˜ on pine (Pinus edulis), and limber pine (Pinus flexilis) at 38 sites, we were able to reconstruct streamflows for the headwaters of the Wind River back to 1672 AD or earlier. The streamflow reconstructions for Bull Lake Creek above Bull Lake; the Little Popo Agie River near Lander, Wyoming; and Wind River near Dubois, Wyoming explained between 40% and 64% of the observed variance, and these extended records performed well in a variety of statistical verification tests. The full reconstructions show pronounced inter-annual variability in streamflow, and these proxy records also point to the prevalence of severe, sustained droughts in this region.These reconstructions indicate that the 20th Century was relatively wet compared to previous centuries, and actual gage records may capture only a limited subset of potential natural variability in this area. Further analyses reveal how tree-ring based reconstructions for small tributary and headwaters gages can be strongly influenced by the length and quality of calibration records, but this work also demonstrates how the use of a spatially extensive network of tree-ring sites can improve the quality of these types of reconstructions.