Ground water occurrence, movement, and its contribution to streamflow were investigated in Loch Vale, an alpine catchment in the Front Range of the Colorado Rocky Mountains. Hydrogeomorphologic mapping, seismic refraction measurements, and porosity and permeability estimates indicate that talus slopes are the primary ground water reservoir, with a maximum storage capacity that is equal to, or greater than, total annual discharge from the basin (5.4 ± 0.8 × 106 m3). Although snowmelt and glacial melt provide the majority of annual water flux to the basin, tracer tests and gauging along a stream transect indicate that ground water flowing from talus can account for ≥75% of streamflow during storms and the winter base flow period. The discharge response of talus springs to storms and snowmelt reflects rapid transmittal of water through coarse debris at the talus surface and slower release of water from finer‐grained sediments at depth. Ice stored in permafrost (including rock glaciers) is the second largest ground water reservoir in Loch Vale; it represents a significant, but seldom recognized, ground water reservoir in alpine terrain. Mean annual air temperatures are sufficiently cold to support permafrost above 3460 m; however, air temperatures have increased 1.1° to 1.4°C since the early 1990s, consistent with long‐term (1976–2000) increases in air temperature measured at other high‐elevation sites in the Front Range, European Alps, and Peruvian Andes. If other climatic factors remain constant, the increase in air temperatures at Loch Vale is sufficient to increase the lower elevational limit of permafrost by 150 to 190 m. Although this could cause a short‐term increase in streamflow, it may ultimately result in decreased flow in the future.

The United States (U.S.) National Park Service has initiated research on the atmospheric deposition and fate of semi-volatile organic compounds in its alpine, sub-Arctic, and Arctic ecosystems in the Western U.S. Results for the analysis of pesticides in seasonal snowpack samples collected in spring 2003 from seven national parks are presented herein. From a target analyte list of 47 pesticides and degradation products, the most frequently detected current-use pesticides were dacthal, chlorpyrifos, endosulfan, and gamma-hexachlorocyclohexane, whereas the mostfrequently detected historic-use pesticides were dieldrin, alpha-hexachlorocyclohexane, chlordane, and hexachlorobenzene. Correlation analysis with latitude, temperature, elevation, particulate matter, and two indicators of regional pesticide use reveal that regional current and historic agricultural practices are largely responsible for the distribution of pesticides in the national parks in this study. Pesticide deposition in the Alaskan parks is attributed to long-range transport because there are no significant regional pesticide sources. The percentage of total pesticide concentration due to regional transport (%RT) was calculated for the other parks. %RT was highest at parks with higher regional cropland intensity and for pesticides with lower vapor pressures and shorter half-lives in air.

The Rocky Mountains in the USA and Canada encompass the interior cordillera of western North America, from the southern Yukon to northern New Mexico. Annual weather patterns are cold in winter and mild in summer. Precipitation has high seasonal and interannual variation and may dier by an order of magnitude between geographically close locales, depending on slope, aspect and local climatic and orographic conditions. The region's hydrology is characterized by the accumulation of winter snow, spring snowmelt and autumnal base¯ows. During the 2±3-month`spring runo' period, rivers frequently discharge 470% of their annual water budget and have instantaneous discharges 10±100 times mean low¯ow.Complex weather patterns characterized by high spatial and temporal variability make predictions of future conditions tenuous. However, general patterns are identi®able; northern and western portions of the region are dominated by maritime weather patterns from the North Paci®c, central areas and eastern slopes are dominated by continental air masses and southern portions receive seasonally variable atmospheric circulation from the Paci®c and the Gulf of Mexico. Signi®cant interannual variations occur in these general patterns, possibly related to ENSO (El NinÄ o±Southern Oscillation) forcing.Changes in precipitation and temperature regimes or patterns have signi®cant potential eects on the distribution and abundance of plants and animals. For example, elevation of the timber-line is principally a function of temperature. Palaeolimnological investigations have shown signi®cant shifts in phyto-and zoo-plankton populations as alpine lakes shift between being above or below the timber-line. Likewise, streamside vegetation has a signi®cant eect on stream ecosystem structure and function. Changes in stream temperature regimes result in signi®cant changes in community composition as a consequence of bioenergetic factors. Stenothermic species could be extirpated as appropriate thermal criteria disappear. Warming temperatures may geographically isolate cole water stream ®shes in increasingly con®ned headwaters. The heat budgets of large lakes may be aected resulting in a change of state between dimictic and warm monomictic character. Uncertainties associated with prediction are increased by the planting of ®sh in historically ®shless, high mountain lakes and the introduction of non-native species of ®shes and invertebrates into often previously simple food-webs of large valley bottom lakes and streams. Many of the streams and rivers suer from the anthropogenic eects of abstraction and regulation. Likewise, many of the large lakes receive nutrient loads from a growing human population.We concluded that: (1) regional climate models are required to resolve adequately the complexities of the high gradient landscapes; (2) extensive wilderness preserves and national park lands, so prevalent in the Rocky Mountain Region, provide sensitive areas for dierentiation of anthropogenic eects from climate eects; and (3) future research should ...