Winter Rain versus Snow in Headwater Catchments: Responses of an Unconfined Pumice Aquifer, South-Central Oregon, USA

Winter precipitation in two headwaters catchments (elevation ~1600 m) in the rain shadow of the Cascades volcanic arc in south-central Oregon normally falls as snow. However, in water year 2015, winter precipitation fell mainly as rain. An eight year study of the unconfined pumice aquifer allowed inter-annual comparison of groundwater recharge during the freshet and discharge during the growing season. During these water years precipitation ranged from 67% (WY2014) to 132% (WY2017) of the 30 year average, and included the rain dominated winter of WY2015 when precipitation during the water year was 98% of the 30 year average. Change in storage in the pumice aquifer was estimated from thickness of the pumice deposit and depth to water table from the ground surface. Measurements were made where 1) the pumice aquifer was exposed at the surface; 2) where the aquifer was partially eroded and overlain by either alluvium or lacustrine glassy silt to fine sand; 3) fens where the partially eroded aquifer was overlain by peat; and 4) monitoring wells drilled through the pumice aquifer into bedrock. In all settings, groundwater storage in the pumice aquifer following the rain-dominated winter of WY2015 was similar or less than storage following the drought of WY2014 when winter precipitation fell as snow. Storage at the end of WY2014 and WY2015 was the least observed in the eight year study. Winter-time rain during WY2015 produced runoff rather than storage in snow pack. Runoff conveyed from the catchments by flow in stream reaches normally dry from late summer through the winter months. Rain-dominated winter precipitation stresses the perched pumice aquifer. Winter storms starting as rain and turning late to snow and ground-freezing temperatures lead to runoff during the next rain-dominated precipitation event. These patterns produced stream flow in channels that are commonly dry during the winter, reduced near-surface groundwater storage in the pumice aquifer, muted springtime freshet, and stressing of groundwater-dependent ecosystems, forage in meadows, and forest health.

of snow pack during the fall and winter while in WY2015 winter precipitation fell primarily as rain. The primary questions addressed in this paper are: What was the response of the pumice aquifer to rain-dominated winter precipitation? What does this response suggest about groundwater availability in this area under changing climate conditions?

Characteristics of Catchments
The two forested catchments considered in this study lie at elevations greater than 1590 m within the Walker Rim study area ( Figure 1). The first catchment, the upper Jack Creek catchment (

Data Sources
Groundwater data were gathered from 22 nested piezometers installed by The Nature Conservancy and Fremont-Winema National Forest at three fens [9] [11], clusters of three monitoring wells screened at different depths at these fens and a single, isolated monitoring well screened to a depth of 15 m [12], and 67 single piezometers (commonly 2 m deep) installed in holes hand augered to determine stratigraphy of alluvial, lacustrine, and pumice deposits. These data were grouped into four categories: 1) piezometers where the pumice deposit was unconfined and exposed at the surface; 2) piezometers screened in the partially eroded pumice aquifer where it was variably confined by alluvial or lacustrine deposits; 3) fens where the pumice aquifer was confined by peat; and 4) monitoring wells completed in underlying bedrock units.
From WY2011 through WY2015 and WY2017, depth to water table was measured between 1-June and 4-June (herein referred to as 1-June) and at the end of the water year (late September) or early in the next water year (October).
In addition, depth to water

Results
Groundwater in the pumice aquifer resides in two distinctly different settings: 1) in pore spaces between pumice grains and 2) in vesicles within pumice grains.
Groundwater within the pore spaces between pumice grains moves freely. Weatherford and Cummings [10] used pressure transducers to demonstrate the isotropic character of the pumice aquifer where it is comprised of undisturbed Plinian fall. The spacing between pressure transducers was 400 m. Over a period of 106 days the greatest percent difference in change at each transducer for every 30 minute interval was 0.057% [13]. The second setting for groundwater is within pumice grains. Klug et al. [14] determined the physical properties of pumice The Forest Service local road 510 (FSLR 510) piezometer (A on Figure 2) was selected to represent this group because the site was located 1) in an area of low local relief (approximately 8 m within a circle with1 km radius centered on the piezometer); 2) excessively drained soil from pumice parent material; 3) pumice thickness of 229 cm; and 4) the auger hole penetrated the underlying paleosol (8 cm) before encountering olivine basalt bedrock.
The hydrograph for the FSLR 510 site is presented in Figure 3. Table 1 presents precipitation data for the Chemult Alternate SNOTEL Site for the same time span. This table also includes the snow-water equivalent (SWE) on 1-April, total precipitation received by 1-April, and the percent of the water year precipitation received by 1-April. On 1-June in two years (WY2011 and WY2012, Figure 3), years when annual precipitation exceeded the 30-year average, SWE was nearly 20 cm on 1-April, and more than 80% of the total precipitation had fallen by 1-April (Table 1), the water table was nearer surface than in two years (WY2013 and WY2014) when the annual precipitation was less than the 30-year average, SWE on 1-April was zero, and less than 80% of annual precipitation was received before 1-April. For purposes of comparison, WY2011 and WY2012 are herein called "wet" years and WY2013 and WY2014 are "dry" years. WY2015, the year when winter precipitation fell mainly as rain, the annual precipitation amount and percent of precipitation received by 1-April followed the "wet" year pattern, but depth to water table on 1-June and SWE on 1-April followed "dry" year patterns. WY2016 and WY2017, years of above average snow-dominated  A second site that illustrates groundwater response in this group was located near FSLR 460 (B on Figure 2). Here, the water table was consistently deeper

Piezometers Screened in the Partially Eroded Pumice Aquifer Where Confined by Alluvial or Lacustrine Deposits
The second group of piezometers includes those installed in auger holes used to determine stratigraphy in ephemeral stream valleys and lake beds cut into the pumice deposit. This group also includes three sites where the uneroded pumice deposit was covered by alluvium. After the eruption of Mount Mazama the drainage network began to evolve. Streams followed the pre-eruption landscape landscape. The Round Meadow system illustrates this environment [10] [13]. In these environments the upper pumice unit was absent and the eroded surface cut into the lower pumice was overlain by lag sand. Above the lag sand was rounded pumice that settled through the water column. This, in turn, was overlain by diatom-bearing glassy silt and fine-grained sand that graded upward to organic-bearing silt. Here, the aquifer includes remnants of the lower pumice deposit, the lag sand, and the water-settled, rounded-pumice deposit. In both settings, the fine-grained deposits that overlie the hybrid aquifer (pumice, lag sand, ±settled pumice) isolate to varying degrees surface water from groundwater in the aquifer [10] [13].
Forty-four single piezometers were used to monitor ground water levels and   The depth to water table on 1-June follows patterns similar to those observed at sites described in Section 4.1. In "wet" years (WY2011 and WY2012) the water table on 1-June was above or near the surface while in "dry" years (WY2013 and WY2014) the water table on 1-June was greater than 80 cm below ground surface. Again, WY2015 follows the "dry" pattern, but has an even deeper water table on 1-June than the drought year of WY2014. The pattern for WY2016 and WY2017 were similar to the "wet" years, but the water table did not reach the surface. The frequency of measurements in WY2011 allowed a change in rate of recession to be detected that mirrored the depth of water table relative to the depth of the contact between fine-grained alluvium, lag sand, and pumice deposit. From 1-June to 12-August the rate of decline was 1.3 cm/day while the water table was in the heavily rooted zone hosted by alluvium. From 12-August to 20-October the rate of recession was 0.7 cm/day while the water table was hosted within the pumice aquifer. Recharge in "dry" years was not enough to raise the water table into the alluvium, rather the water table remained within the pumice deposit during those years. The recharge was even less in WY2015. Although the hydrograph in Figure 6 for this site shares patterns similar to the alluvial site described above, there are several differences. These differences appear to reflect the influence of the bedrock-line ephemeral stream valley that enters the meadow near this piezometer. These differences include the following.
1) The water table in each water year was hosted in the lacustrine/alluvial sediments that overlie the hybrid pumice aquifer on 1-June. On dates when the depth to water table was measured before 1-June, the water table was near the ground surface. 2) Recession rates ranged from 0.71 cm/day in WY2011 to 1.23 cm/day in WY2013. This is distinct from most alluvial/lacustrine sites where the recession rate in WY2011, a "wet" year, is greater than those in "dry" years such as WY2013. 3) In WY2015, the early season recession rate was considerably lower than near the end of the water year. Access to the site was possible on 7-March-2015 in the morning while roads were still frozen. Between this date and 3-June, the recession rate was 0.34 cm/day with the water table within 3 cm of ground surface on 7-March when the ephemeral stream was still flowing. The recession rate was greater from 3-June to the end of the water year with an estimated recession rate of 1.19 cm/day. 4) The depth to water table at this site ( Figure 6) shows the greatest response to precipitation of the piezometer network. The depth to water table was measured on 4-September in WY2012 (-122 cm) and estimated for 30-September (−145 cm, measured dry at −144 cm). An early season storm moved through the area on 15/16-October dropping 2.8 cm of rainfall at the Chemult Alternate SNOTEL Site. Following this event, the water table was measured at −121 cm below ground surface on 20-October ( Figure  6). Few piezometers responded to this storm event.

Relations between Depth to Water Table on 1-June and Recession Rates
A relation between recession rate of the water table and subsurface storage on 1-June is suggested by data from all piezometers measured in this study. These findings are consistent with findings reported by Garcia and Tague [6] for three Journal of Water Resource and Protection catchments in the western United States. Data for piezometers located where the pumice aquifer was exposed at the surface (Section 4.1) are presented in Figure   7 and similar data for those located where alluvium or lacustrine sediments overlie the partially eroded pumice aquifer (Section 4.2) are presented in Figure   8. Several observations arise from these plots. 1) The water table at sites plotted in Figure 7 remained below the ground surface at all sites in all years while

Fens where the Pumice Aquifer Is Confined by Peat Deposits
The internal stratigraphy of five fens was described by Cummings et al. [9] and Weatherford and Cummings [10] and the biodiversity and environmental flows and levels were presented by Aldous et al. [11] and Aldous and Bach [15]. The morphology of fens was characterized by a sloping surface underlain by peat which locally graded laterally to organic-rich fine-grained sandy silt with medium-to coarse-grained rounded pumice sand. These materials form the upper confining layer to the pumice aquifer. Peat was thickest (~1.2 m) where the potentiometric surface in the underlying pumice aquifer was above ground surface during much of the growing season. However, in "dry" years and especially in WY2014 and WY2015 the potentiometric surface in some fens was below the ground surface throughout the growing season and locally retreated below the confining layer [10]. Under these conditions, the bryophyte-rich plant community that dominated these fens turned brown and the normal springy nature of the ground surface decreased.
An erosion surface marked the contact between the peat or organic-rich sandy silt confining layer and the underlying pumice aquifer. This contact cut downward through the pumice deposit and locally to the pre-eruption surface. In some fens, piping features rose from the pumice aquifer through the peat confining layer and discharged groundwater to low-volume streams which flowed across the peat surface. Focused discharge from these streams and diffuse discharge through the fen surface accumulated in small pools or streams at the toe of the fen. This discharge contributed to perennial stream flow in the upper reaches of Jack Creek. However, locally, the discharge ponded against low-relief berms that marked the surface boundary between the fen and neighboring alluvium-floored, ephemeral stream valleys [10]. These berms were spatially asso-Journal of Water Resource and Protection ciated with iron cementation in the underlying remnants of the pumice aquifer.
Nested piezometers were installed in three fens (Wilshire, Johnson Meadow, and Dry Meadow) by The Nature Conservancy in collaboration with the Fremont-Winema National Forest [11] to estimate environmental flows and levels.
Later, single piezometers were installed in areas neighboring these fens to provide context to the fen environment. In addition, single piezometers and piping features were monitored in four additional fens. The hydrographs varied considerably within an individual fen, among fens, and between the fens and adjacent areas. These differences are described in Aldous et al. [11], Cummings et al. [9] and Weatherford and Cummings [10]. Groundwater that diffusely discharged through the fen surface was from the pumice aquifer. However, the source of this groundwater included groundwater flowing through the pumice aquifer from the melting of annual snowpack and, to varying degrees, groundwater flowing along bedrock contacts and along faults [9] [10] [11]. These additional sources of groundwater modify the groundwater recession pattern. In fens, the recession rate for the pumice aquifer is lower until late July to early August and increases from that time through the end of the water year. cm, respectively [16]. Both piezometers were screened in the pumice aquifer.
The water level in the W6-1.4 piezometer was consistently above the ground surface throughout all water years while, higher on the slope, the W5-1.4 was above the ground surface into August, but dropped below the ground surface by

Monitoring Wells
Ten wells were drilled by the U.S. Forest Service to monitor ground water levels [12]. Piezometers were installed in three closely spaced wells at each of three fens: Johnson Meadow fen, Wilshire fen, and Dry Meadow fen (Figure 2). An additional single well was drilled and piezometer installed in a broad low relief forested area where the pumice aquifer was known to contain water throughout the growing season (Section 5 monitoring well in Figure 2). At the fen sites,  cm diameter core was recovered. Piezometers were installed in each well in sections interpreted to be potential aquifers [12].
At the three fens, the wells were upslope from the "wetland on dry ground amongst Lodgepole pine trees" [12]. The distance between the wells and the   Figure 10 contains the hydrograph for Wilshire 1 at the Wilshire fen ( Table 2). The well was spudded in the soil horizon developed from pumice and therefore was similar to the hand-augered holes described in In general, for monitoring wells, the greatest recession occurred in WY2014 and WY2015 when water tables on 30-September were 25 to 37 cm lower, respectively, than the first measured date (10-Ocotober-2010) at the three fens.
The recession was less in the single isolated well where the water table declines were only 11 and 14 cm, respectively, compared to 10-October-2010.

Surface Water
The two catchments had relatively minor surface water resources. The largest Figure 10. Hydrograph for Wilshire 1 monitoring well at the Wilshire fen (Zone 10, 0613717E, 4795181N). Initial date of measurement was 10-October-2010, 7 days after the well was drilled and piezometer installed [12]. Gray triangles are depths to water table from the top of the piezometer measured 1-June or 30-September. Red squares are calculated depths to water table for 1-June or 30-September assuming recession was linear. The ephemeral drainage network conveyed water during the freshet in "wet"

Precipitation Patterns
Change in storage in the pumice aquifer follows annual precipitation patterns.
During the water years considered in this study, maximum storage was attained in April/May followed by steady decline to minimum storage in Septem-Journal of Water Resource and Protection  (Figure 13(a)), a "wet" year (Table 1), and 7-January-2015 (Figure 13(b)), the water year when winter precipitation fell primarily as rain. Figure 14 compares precipitation data from the Chemult Alternate SNOTEL station for WY2015 to the 30 year (WY1981-WY2010) average cumulative precipitation curve and the median snow water equivalent curve. Although the cumulative precipitation curve from October to March is above the 30-year average, the SWE curve indicates the precipitation was received primarily as rain.
In addition to precipitation data for the Chemult Alternate SNOTEL station during the study years, records of ground temperature were available within the study area at 50 cm below ground surface within the pumice deposit (Section 4.1 setting). An Onset temperature/relatively humidity logger recorded conditions at least every 60 minutes. Table 4 reports the date for each water year when warming started at 50 cm below ground surface and the ground temperature on that date and on 1-June. The instrumented site was located in a flat area in   Lodgepole pine forest. Short-lived (often less than 12 hours) negative deflections in the curves were produced during rain events when water that was colder than the ground migrated downward along the PVC pipe and chilled the cavity where the sensor was located. These deflections occur during approximately the first 75 days of each water year, but are particularly common in WY2015 ( Figure 15).
During that year, prominent deflections occurred until 8-December-2014. It is assumed by that date the ground around the PVC pipe had frozen and cold rain water no longer had an easy route to travel along. However, compared to other years, temperature fluctuations are common throughout the winter months. The spring of WY2015 was characterized by the earliest onset of warming at 50 cm Journal of Water Resource and Protection Figure 15. Temperature recorded every 60 minutes at 50 cm depth using Hobo U23 Pro v2 temperature/relative humidity data loggers during the months of October, November, and December in WY2015. Each negative deflection is associated with a rain event recorded at Chemult Alternate SNOTEL Site (http://www.wcc.nrcs.usda.gov/nwcc/site?sitenum=395). After 8-December freezing of the ground surface around the PVC pipe apparently stopped cold rain water from moving downward to the depth of the temperature probe.
depth  and the highest ground temperature on 1-June (Table 4).

Discussion
The occurrence of groundwater and the flow pathways it follows in volcanic rocks are controlled by structure, the stratigraphy and physical properties of volcanic units and associated volcaniclastic sedimentary deposits, and the geomorphologic evolution of the volcanic landscape. Examples of the complexities that arise in volcanic systems are described throughout the world (e.g. [17] [18] [19]). In the study area, the blanket of Plinian fall overlying relatively low permeability bedrock units [12] reduces these complexities and allows examination within the aquifer that locally restricted lateral flow [10].
The expected annual pattern of snow accumulation during winter months, rapid springtime melting and recharge of the pumice aquifer, and discharge by evapotranspiration during the summer growing season did not occur in WY2015 when winter precipitation fell primarily as rain. Recharge of the pumice aquifer in WY2015 (Figures 3-6) when cumulative precipitation was above average (Figure 14) was similar to WY2014 ( Figure 16) when, for the same time period, cumulative precipitation was near record lows. A measure of recharge and discharge from the aquifer is provided by change in storage expressed as percent of the total thickness (pumice only sites or pumice plus overlying sediments sites) saturated at the start of each water year (1-October) and on 1-June (   In this discussion, we will consider the inter-annual variations in storage in the pumice aquifer in relation to precipitation patterns. The focus will be on three water years; 1) WY2013, 2) WY2014, a year of severe drought, and 3) WY2015 when winter precipitation was rain dominated. This is followed by discussion of rain-versus snow-dominated winter precipitation in this landscape.

WY2013
Water year 2013 was the first of three water years when SWE was zero and the percentage of annual precipitation received was below 80% on 1-April. This water year was preceded by two water years when annual precipitation was above the 30-year average (  [20]. The first site visits were on 26-27-April when it was observed that the stream network was dry and there was no evidence of flow in these channels during the freshet. Discharge on Jack Creek at FSCR 8821 was 0.87 m 3 ·s −1 and the channel was dry by 7-July (Table 3).
Sixteen (16) percent of the annual precipitation fell during the last six months of WY2012 (Table 1). The dry summer depleted groundwater storage in the aquifer below levels in the previous "wet" years. Although the impact on storage was not great, a few percent of aquifer thickness (Table 5), lower storage at the start of the water year combined with less springtime recharge produced declines in storage in each of the following water years through the start of WY2016 (end of WY2015). This is particularly noted at sites where remnants of the pumice aquifer are overlain by alluvium (e.g. east tributary valley, Figure 5) and to a lesser extent at sites where the pumice aquifer is exposed at the surface (e.g. FSLR 510, Figure 3). Deeper water tables on 1-June, characteristic of WY2013 and the following two years, are associated with lower recession rates during the growing season (Table 5). Early snow melt (SWE = 0 on 1-April, Table 1) was reflected in warming of the ground at 50 cm (Table 4) four to six weeks earlier than warming in "wet" years (Table 4). Earlier warming is noted in the three years when SWE = 0 on 1-April. However, this pattern persisted in subsequent water years when snow cover remained after 1-April (WY2016 and WY2017; Table 4). This is particularly noted in WY2017 when 87 percent of the annual precipitation had fallen by 1-April, precipitation was 23 cm above the 30-year average, and winter precipitation fell mainly as snow (Table 1).
In fen environments, groundwater levels peripheral to the main area of upflow experienced declines in water levels ( Figure 9). However, in these peripheral areas the water table remained near surface within the confining peat layers throughout the growing season. Within the prominent up flow zones and at lower elevations within the fens the potentiometric surface remained above the ground surface as indicated for the W6-1.4 piezometer at the Wilshire fen ( Figure 9).  Figure 13 therein).

WY2015, Winter Precipitation Dominated by Rain
The study area followed precipitation patterns throughout the western United States where there was exceptionally low snowpack in WY2015 [20]. Although precipitation received at the Chemult Alternate SNOTEL Site was above the 30 year average until late February (Figure 14), snow cover was minimal in January ( Figure 13(b)), SWE was zero on 1-April, and 76 percent of annual precipitation had been received by 1-April (Table 1). The rain-dominated winter precipitation foreshadows climate change scenarios for the Pacific Northwest [2] [4] [5].
Although winter access to the study area in most years was by snow machines, in WY2015 access by sports utility vehicles was possible throughout the winter ( Figure 11), but was restricted during the spring thaw when frost was coming out and roads constructed with native material (pumice) were impassable. Our first visit was 7-March-2015 when access was possible during the morning when the roads were still frozen.
Although precipitation, mainly as rain, was greater than the 30-year average during the first 4.5 months of the water year, storage in the pumice aquifer on 1-June was similar to storage on 1-June in WY2014 when record low precipitation was received as snow during the same time span (Table 5)

Rain versus Snow and Recharge of the Pumice Aquifer
The rain-dominated winter of WY2015 in the study area coincided with snow drought in the western United States. Snow records west of 115˚W for 1-April found the lowest ever recorded SWE at 81% of stations with at least 40 years of record [20]. Mote et al. [20] argued that human influence and sea surface temperature anomalies contributed to the snow drought in Oregon and Washington. Cooper et al. [3] tested whether the sensitivity of Cascades snowpacks during this snow drought could serve as an analog for climate warming. They reported the 2014 and 2015 winter air temperature anomalies were approximately +2˚C and +4˚C, respectively, above the climatological mean. By comparing model predictions to field based observations they concluded that only the modeled basin-mean peak SWE resembled predicted values based on modeled sensitivities. They concluded that magnitude and phasing of winter precipitation events rather than just air temperature controlled date of peak SWE, duration of snow cover, and snow disappearance date.
Although changing climate in the Pacific Northwest is expected to produce shifts toward less snow, more rain, and early snowmelt [2] [4] [5] the analysis of Cooper et al. [3] raises important factors that contribute to changes in system dynamics in the Cascades. Our study area lies in the rain shadow of the Cascades Range. The elevation (1590 to 1760 m) is higher than most pass elevations in the Cascades Range, but its location in the rain shadow results in significantly less total precipitation and colder air temperatures. These differences are reflected in oxygen-hydrogen isotopic ratios for precipitation in the Cascades versus the highlands that lie east of the Cascades crest [10] [21].
The three water years marked by zero SWE on 1-April at the Chemult Alternate SNOTEL Site, relatively lower recharge of the pumice aquifer, and the lowest storage at the end of the water year are different in terms of snow-versus rain-dominated winter precipitation. In WY2013 and WY2014 the annual precipitation was below the 30-year average, but fell primarily as snow. Low recharge of the aquifer during the freshet was related to low snow pack. In WY2015, winter precipitation was above the 30-year average through much of the winter, but primarily as rain. Stream flow leaving the upper Jack Creek basin in December and January ( Figure 11) removed water that would normally have been stored in snowpack until the freshet. Data from our instrument station located in the study area suggests early winter rain-dominated storms followed by freezing temperatures produced frozen ground that limited infiltration and encouraged runoff. By the middle of December, 2014, the ground had frozen as suggested by the deflections noted in temperature records at 50 cm depth ( Figure 15 Potentially, climate change scenarios of more frequent snow-and rain-dominated and rain-dominated winters [2] [4] [5] will stress this perched, near-surface source of groundwater in the rain shadow of the Cascades Range. The pattern of storms starting as rain and turning late to snow and ground-freezing temperatures leads to runoff during the next rain-dominated precipitation event. These patterns suggest an increasing number of years with winter stream flow in channels that are currently dry, reduced near-surface groundwater storage in the pumice aquifer because of increased winter time runoff, muted springtime freshet similar to "dry" water years like WY2013 and WY2014, and more frequent stressing of groundwater-dependent ecosystems, forage in meadows, and forest health (e.g. [22]).

Conclusions
Groundwater storage in the unconfined and partially confined pumice aquifer follows annual precipitation patterns with the maximum storage following the spring freshet and minimum storage near the end of the water year and start of the next water year.
The highest recession rates of the water table occurred where alluvium overlies the partially eroded pumice aquifer and the water table on 1-June was within the rooted zone. Lower recession rates were noted where the 1-June water table was within the pumice aquifer but below the main rooting zone for most plants.
Lower recession rates were noted in "dry" years when the 1-June water table was deeper in the pumice aquifer than in "wet" years when the 1-June water table was near the surface.
Water years characterized by deeper water tables on 1-June received less than 80% of precipitation by 1-April and had zero SWE on 1-April.
Maximum storage and change in storage during the growing season in the pumice aquifer following the rain-dominated precipitation pattern of WY2015 was similar to patterns observed in the "dry" water years of WY2013 and WY2014 even though total precipitation was near the 30-year average.
Rain-dominated winter storms followed by cold temperatures in WY2015 produced freezing of the ground surface and contributed to runoff during the winter months. The lack of water storage in snowpack contributed to weak recharge of the pumice aquifer during the freshet, anomalously low stream flow on 1-June, and deep water tables throughout the growing season. These factors contributed to drying of peat layers and local desiccation in fens, reduced forage in meadows, and reduced discharge from springs. Similar patterns were observed in the severe drought of WY2014.