Extreme precipitation events (EPEs), a key class of hydrometeorological extremes, are intensifying globally under climate change; however, their effects on water-table dynamics across varying soil textures remain poorly understood. To better understand the impacts of EPEs, we conducted one-dimensional modeling to evaluate water-table response time, displacement, recession time, and total recharge under EPEs of 0.20 m, 0.40 m, and 0.60 m amounts, applied over 1-, 7-, and 20-day durations across twelve soil textures. The results show that coarse soils (i.e., sand) respond within days, while fine soils (i.e., clay) may take over 200 days. Water-table displacement ranged from 0.30 to 1.64 m and increased with EPE magnitude. The time it took for water tables to recede ranged from 1.2 to 3.0 years. A first-order estimate of total possible recharge, calculated from porosity and displacement, ranged from 17% (clay) to 97% (sand), averaging similar to 63% across soil textures. These findings highlight that recharge is primarily governed by EPE magnitude and soil properties, not event duration. This modeling effort provides new insight into how soil texture modulates groundwater response to extreme precipitation, informing future water budget and resilience assessments.

Due to a lack of management operations data, hydrological models may represent reservoirs as natural lakes, leading to poor discharge predictions in regulated basins. To parse seasonal operational signatures, we compare the dynamics of natural lake and reservoir systems across North America using Surface Water and Ocean Topography (SWOT) satellite observations and derived discharge estimates. Overall, reservoirs and their adjacent river reaches exhibit significantly greater variability (in standard deviation) than their natural counterparts across almost all SWOT observed (e.g. water surface elevation) and inferred (e.g. discharge) variables. Natural lakes show strong same-day correlations between inflow and outflow discharge (median Spearman R = 0.8), whereas 76% of reservoirs exhibit maximum correlation when outflow is lagged, suggesting operations buffer seasonal flow variability. Our findings indicate operations not only affect reservoir dynamics themselves but also have upstream and downstream consequences, which, when integrated into models, will offer more realistic hydrologic conditions.

The lack of comprehensive water supply prediction capacity in most areas of the U.S. poses challenges in evaluating water availability. In order to improve water availability prediction and assessment, in 2019, the U.S. Geological Survey initiated planning efforts to intensively study five medium-sized basins throughout the U.S. over the next decade, including the Upper Colorado River Basin (UCOL). Research in the UCOL aims to provide insight into how past, present, and future snow conditions – including amount, timing, melt, and transitions from snow- to rain-dominated systems – impact water supply (quantity and quality) and the ability to meet demand. A specific emphasis is placed on how these processes affect water budget components and dissolved solids concentration and loading in the UCOL. A fully integrated groundwater-surface water hydrologic model (GSFLOW), and temporally dynamic dissolved solids models (SPARROW) that explicitly represent the groundwater contribution to dissolved solids loading to streams are being applied to meet the study objective. Comprehensive information on water diversion and groundwater pumping has been compiled and is being explicitly represented in the models to better represent human demand. Temporal and spatial patterns in predicted water quantity and quality conditions are being evaluated in the context of past and projected future changes, summarized over 30-year time periods, in snow metrics. Historical trends in multiple snow metrics, water budget components, groundwater levels, and dissolved solids provide context for evaluations of current conditions and motivation for further investigation and modeling. The tools and concepts developed in the UCOL will contribute to ongoing work in the other regional study basins as well as a forthcoming national water availability assessment.

Study region: Headwaters of the upper Colorado River basin (UCOL), USA Study focus: Surface-water and groundwater numerical models incorporating water-use information were used to investigate changes in climate, water use, and simulated hydrologic responses of snow processes, evapotranspiration, groundwater, and streamflow during recent wet (1982-1999) and drought (2000-2022) periods in the headwater subregions of the upper Colorado River basin. New hydrologic insights for the region: Decreases in average streamflow between wet and drought periods ranged from 20 % in the Colorado River headwaters subregion to 23 % in the Gunnison River headwaters subregion. Like streamflow, average surface runoff was statistically less during the drought than the wet period, with decreases from 24-31 % in the headwaters. On a volume basis, runoff decreases were greater than streamflow decreases in both the Colorado River and Gunnison River headwaters. Although the amount of water-year groundwater discharge to streams remained nearly the same between the wet and drought periods, groundwater as a percentage of streamflow increased between the wet and drought periods, highlighting the importance of groundwater in sustaining streamflow during drought conditions. Multiple linear regression analyses revealed that snowmelt-only models were better than the best precipitation and temperature models at explaining streamflow variability from all headwater subregions for both the wet and drought periods.

Because use of high-resolution hydrologic models is becoming more widespread and estimates are made over large domains, there is a pressing need for systematic evaluation of their performance. Most evaluation efforts to date have focused on smaller basins that have been relatively undisturbed by human activity, but there is also a need to benchmark model performance more comprehensively, including basins impacted by human activities. This study benchmarks the long-term performance of two process-oriented, high-resolution, continental-scale hydrologic models that have been developed to assess water availability and risks in the United States (US): the National Water Model v2.1 application of WRF-Hydro (NWMv2.1) and the National Hydrologic Model v1.0 application of the Precipitation-Runoff Modeling System (NHMv1.0). The evaluation is performed on 5390 streamflow gages from 1983 to 2016 (similar to 33 years) at a daily time step, including both natural and human-impacted catchments, representing one of the most comprehensive evaluations over the contiguous US. Using the Kling-Gupta efficiency as the main evaluation metric, the models are compared against a climatological benchmark that accounts for seasonality. Overall, the model applications show similar performance, with better performance in minimally disturbed basins than in those impacted by human activities. Relative regional differences are also similar: the best performance is found in the Northeast, followed by the Southeast, and generally worse performance is found in the Central and West areas. For both models, about 80 % of the sites exceed the seasonal climatological benchmark. Basins that do not exceed the climatological benchmark are further scrutinized to provide model diagnostics for each application. Using the underperforming subset, both models tend to overestimate streamflow volumes in the West, which could be attributed to not accounting for human activities, such as active management. Both models underestimate flow variability, especially the highest flows; this was more pronounced for NHMv1.0. Low flows tended to be overestimated by NWMv2.1, whereas there were both over and underestimations for NHMv1.0, but they were less severe. Although this study focused on model diagnostics for underperforming sites based on the seasonal climatological benchmark, metrics for all sites for both model applications are openly available online.

Schema representing UV-induced signaling, rapamycin and PHT-427-regulated pathways in keratinocytes.

First posted August 23, 2023 For additional information, contact: Director, South Atlantic Water Science CenterU.S. Geological Survey1770 Corporate Drive, Suite 500Norcross, GA 30093Contact Pubs Warehouse This report documents a three-part continental-scale calibration procedure and a new streamflow routing algorithm using the U.S. Geological Survey National Hydrologic Model (NHM) infrastructure along with an application of the Precipitation-Runoff Modeling System (PRMS). The traditional approach to hydrologic model calibration and evaluation, which relies on comparing observed and simulated streamflow, is not sufficient for accurately representing the non-streamflow parts of the water budget. If intermediate process variables computed by the hydrologic model are not examined, the variables could be characterized by parameter values that do not replicate those hydrological processes present in the physical system. In answer to this potential problem, alternative hydrologic process variables from the model (in addition to streamflow) are included in a calibration procedure applied to the conterminous United States (CONUS) domain.The three-part calibration procedure presented in this report considers volume (calibration by hydrologic response unit [byHRU]), timing (calibration by headwater watershed [byHW]), and measured streamflow [byHWobs]). The first part, byHRU, is considered a water-balance volume calibration that uses five alternative (non-streamflow) hydrologic quantities (runoff, actual evapotranspiration, recharge, soil moisture, and snow-covered area) as calibration targets for each hydrologic response unit (HRU). These alternative data products were derived, with error bounds, from multiple sources for each of the 109,951 HRUs in the NHM on time scales varying from annual to daily. The second part of the calibration, byHW, is considered a streamflow timing calibration that uses statistically based streamflow simulations developed using ordinary kriging for 7,265 headwater watersheds that had drainage areas of less than 3,000 square kilometers (1,158 square miles) across the CONUS. Two streamflow routing algorithms were tested in this byHW calibration: (1) continuity without attenuation of the flood pulse and (2) a new formulation of the Muskingum routing method, which was added to the PRMS as part of this study. The third part of the calibration, byHWobs, refines the model parameters using available measured streamflow using 1,417 streamgage locations. A multiple-objective, stepwise, automated calibration procedure was used to identify the optimal set of parameters for each calibration procedure.Using a variety of alternative datasets for calibration of the water budget provides users of the NHM-PRMS with improved initial parameters and helps alleviate the equifinality problem (getting the right answer for the wrong reason). Through a community effort, these alternative data products, with error bounds, can be used to improve and expand our understanding of hydrologic-process representation in models. The broader modeling community can use these data products, with error bounds, to calibrate and evaluate hydrologic models using more than streamflow.

Supplemental Figure 1.Percent bias of midsegment of flow duration curve (PBIAS_FDC) maps for National Water Model v2.1 (NWMv2.1)(left; A) and National Hydrologic Model v1.0 (NHMv1.0)(right; B), where PBIAS_FDC >20% or

Floods affected approximately two billion people around the world from 1998–2017, causing over 142,000 fatalities and over 656 billion U.S. dollars in economic losses. Flood data, such as the extent of inundation and peak flood stage, are needed to define the environmental, economic, and social impacts of significant flood events. Ground-based global positioning system (GPS) surveys of post-flood high-water marks (HWMs) and topography are commonly used to define flood inundation and stage, but can be time-consuming, difficult, and expensive to conduct. Here, we demonstrate and test the use of small unmanned aircraft systems (sUAS) and close-range remote sensing techniques to collect high-accuracy flood data to define peak flood stage elevations and river cross-sections. We evaluate the elevation accuracy of the HWMs from sUAS surveys by comparison with traditional GPS surveys, which have acceptable accuracy for many post-flood assessments, at two flood sites on two small streams in the U.S. Mean elevation errors for the sUAS surveys were 0.07 m and 0.14 m for the semiarid and temperate sites, respectively; those values are similar to typical errors when measuring HWM elevations with GPS surveys. Results demonstrate that sUAS surveys of HWMs and cross-sections can be an accurate and efficient alternative to GPS surveys; we provide insights that can be used to decide whether sUAS or GPS techniques will be most efficient for post-flood surveying.

Flood variability due to changes in climate is a major economic and social concern. Climate drivers can affect the amount and distribution of flood-generating precipitation through seasonal shifts in storm tracks. An understanding of how the drivers may change in the future is critical for identifying the regions where the magnitude of floods may change. Here we show the regions in the conterminous U.S. where seasonal changes in global-scale climate oscillations have driven a large part of the variability of flood magnitude. The regions are cohesive across multiple watershed boundaries suggesting that variability in floods is driven by regional climate influences. Correlations with climate indices indicate that floods in the western and southern U.S. are most affected by global-scale climate. The regions provide a useful approach for characterizing flood variability and for attributing climatic drivers on flood variability and magnitude.

Core Ideas We describe an approximation for filtering of periodic infiltration in layered soil. Transitions in soil‐water properties between soil layers affect the filtering. Errors are smaller in soils where changes in soil‐water properties are small. Infiltration and downward percolation of water in the vadose zone are important processes that can define the availability of water resources. We present an approach that provides insight into how periodic infiltration forcings at the land surface filter in a layered vadose zone in terms of changes in the timing and magnitude of hydrologic responses. To represent geologically realistic systems, we used vertical sequences of one‐dimensional periodic solutions, where each solution represents a single soil in a layered profile. The overall approach is based on a linearized Richards equation and assumes that the effects on flow of continuous pressure head changes at soil interfaces are negligible. We evaluated the limit of these approximations by comparison with results from the numerical model HYDRUS‐1D, which uses the full Richards equation. We compared (i) the depth at which flux variations became steady, and (ii) the travel time of wetting fronts to reach a depth of 3 m. The solution was reasonably accurate (error less than a factor of 2) for infiltration cycles with periods from 30 to 365 d and for fluxes common in arid and semiarid environments (0–2 mm d−1). Lag times between a surface forcing and response at any depth were accurate (error less than a factor of 1.1). The approximation generally provided consistent estimates of the damping and time lag, such that it overestimated the depths where fluxes were steady and underestimated the time for a forcing to reach a specific depth.

Increasing demand on groundwater resources motivates understanding of the controls on recharge dynamics so model predictions under current and future climate may improve. Here we address questions about the nonlinear behavior of flux variability in the vadose zone that may explain previously reported teleconnections between global-scale climate variability and fluctuations in groundwater levels. We use hundreds of HYDRUS-1D simulations in a sensitivity analysis approach to evaluate the damping depth of transient recharge over a range of periodic boundary conditions and vadose zone geometries and hydraulic parameters that are representative of aquifer systems of the conterminous United States (U.S). Although the models were parameterized based on U.S. aquifers, findings from this study are applicable elsewhere that have mean recharge rates between 3.65 and 730 mm yr(-1). We find that mean infiltration flux, period of time varying infiltration, and hydraulic conductivity are statistically significant predictors of damping depth. The resulting framework explains why some periodic infiltration fluxes associated with climate variability dampen with depth in the vadose zone, resulting in steady-state recharge, while other periodic surface fluxes do not dampen with depth, resulting in transient recharge. We find that transient recharge in response to the climate variability patterns could be detected at the depths of water levels in most U.S. aquifers. Our findings indicate that the damping behavior of transient infiltration fluxes is linear across soil layers for a range of texture combinations. The implications are that relatively simple, homogeneous models of the vadose zone may provide reasonable estimates of the damping depth of climate-varying transient recharge in some complex, layered vadose zone profiles. (C) 2017 Elsevier B.V. All rights reserved.

We have developed a screening tool to visualize and conceptualize the filtering properties of a layered vadose zone. Climate projections indicate that rainfall timing and magnitude may change and impact groundwater resources. This increases the importance of understanding how the vadose zone filters infiltration variability and ultimately affects recharge and groundwater resources. An approximate solution for the filtering of surface forcings through soil layers was developed previously, and the soil and conditions where its approximations are appropriate was evaluated. Here we present a screening tool based on the solution for estimating how periodic infiltration forcings filter in a layered vadose zone for different soil properties and surface flux conditions. The solutions identify time-varying elements of surface forcings that persist to the depth of the water table, leading to transient recharge. We investigated the filtering properties of the vadose zone in Central Valley, California, and identified areas where surface forcings are essentially damped and recharge can be approximated as steady. We also determined the travel time for infiltration pulses to reach the depth of the water table.

We present a logistic regression approach for forecasting the probability of future groundwater levels declining or maintaining below specific groundwater-level thresholds. We tested our approach on 102 groundwater wells in different climatic regions and aquifers of the United States that are part of the U.S. Geological Survey Groundwater Climate Response Network. We evaluated the importance of current groundwater levels, precipitation, streamflow, seasonal variability, Palmer Drought Severity Index, and atmosphere/ocean indices for developing the logistic regression equations. Several diagnostics of model fit were used to evaluate the regression equations, including testing of autocorrelation of residuals, goodness-of-fit metrics, and bootstrap validation testing. The probabilistic predictions were most successful at wells with high persistence (low month-to-month variability) in their groundwater records and at wells where the groundwater level remained below the defined low threshold for sustained periods (generally three months or longer). The model fit was weakest at wells with strong seasonal variability in levels and with shorter duration low-threshold events. We identified challenges in deriving probabilistic-forecasting models and possible approaches for addressing those challenges.

Abstract The PI3Kinase/Akt/mTOR pathway has important roles in cancer development for multiple tumor types, including UV-induced nonmelanoma skin cancer. Immunosuppressed populations are at increased risk of aggressive cutaneous squamous cell carcinoma (SCC). Individuals who are treated with rapamycin (sirolimus, a classical mTOR inhibitor) have significantly decreased rates of developing new cutaneous SCCs compared with those that receive traditional immunosuppression. However, systemic rapamycin use can lead to significant adverse events. Here, we explored the use of topical rapamycin as a chemopreventive agent in the context of solar-simulated light (SSL)-induced skin carcinogenesis. In SKH-1 mice, topical rapamycin treatment decreased tumor yields when applied after completion of 15 weeks of SSL exposure compared with controls. However, applying rapamycin during SSL exposure for 15 weeks, and continuing for 10 weeks after UV treatment, increased tumor yields. We also examined whether a combinatorial approach might result in more significant tumor suppression by rapamycin. We validated that rapamycin causes increased Akt (S473) phosphorylation in the epidermis after SSL, and show for the first time that this dysregulation can be inhibited in vivo by a selective PDK1/Akt inhibitor, PHT-427. Combining rapamycin with PHT-427 on tumor prone skin additively caused a significant reduction of tumor multiplicity compared with vehicle controls. Our findings indicate that patients taking rapamycin should avoid sun exposure, and that combining topical mTOR inhibitors and Akt inhibitors may be a viable chemoprevention option for individuals at high risk for cutaneous SCC. Cancer Prev Res; 9(3); 215–24. ©2016 AACR.

First posted August 18, 2016 Revised April 15, 2019 For additional information, contact: Director, Arizona Water Science CenterU.S. Geological Survey520 N. Park AvenueTucson, AZ 85719http://az.water.usgs.gov/ This study assessed progress toward achieving sustainable groundwater use in the Sierra Vista Subwatershed of the Upper San Pedro Basin, Arizona, through evaluation of 14 indicators of sustainable use. Sustainable use of groundwater in the Sierra Vista Subwatershed requires, at a minimum, a stable rate of groundwater discharge to, and thus base flow in, the San Pedro River. Many of the 14 indicators are therefore related to long-term or short-term effects on base flow and provide us with a means to evaluate groundwater discharge to and base flow in the San Pedro River. The indicators were based primarily on 10 to 20 years of data monitoring in the subwatershed, ending in 2012, and included subwatershedwide indicators, riparian-system indicators, San Pedro River indicators, and springs indicators. Groundwater management actions including voluntary retirement of irrigation pumping in the subwatershed resulted in about a 5,100 acre-feet (acre-ft) reduction in net human use from 2002 to 2012. Subwatershed population increased more than 10,000 during the same period. Most of the reduction occurred during 2002–07 and included reductions in groundwater pumping and increases in managed recharge; net human use varied annually by a few hundred acre-ft during 2007–12. The groundwater budget for 2012 showed a deficit of about 5,000 acre-ft, although the total water-budget uncertainty was about 5,500 acre-ft. In the vicinity of the U.S. Army's Fort Huachuca, regional-aquifer water levels were in steady decline beginning in at least the mid-1990s (in older wells since at least the early-1970s), as the cone of depression centered on the Sierra Vista and Fort Huachuca pumping centers continued to deepen. This was evident in the individual water levels on Fort Huachuca, as well as from the horizontal hydraulic gradients that extend from the pumping centers toward the San Pedro and Babocomari Rivers. Basin water levels in wells southeast of Sierra Vista, away from the river, were also experiencing declines, while some water levels closer to the river were rising. Near-stream vertical gradients along the San Pedro River showed no clear increasing or decreasing trends that would indicate a shift in the direction of subsurface flow between the riverbed and the alluvial aquifer, or a trend in the magnitude of groundwater/surface-water exchange. Annual streamflow permanence data showed no clear change in streamflow permanence trends in any of the river reaches, other than those related to precipitation trends. Similarly, the single-day, dry-season, wet-dry streamflow analysis of all subwatershed river reaches indicated no change in condition over the past 14 years, with the exception of the Hereford reach, which has seen a statistically significant increase in wetted length. Dry-season, alluvial-aquifer water levels in the Hereford reach also showed a statistically significant increase. These improvements are attributed to the end of irrigation pumping in the area. Although data indicate that the length of the Fairbank North wetted reach may be in decline, it is not yet statistically significant. Stable-isotope data indicated reduced groundwater discharge to the Babocomari River in the vicinity of the Babocomari River near Tombstone gaging station and to the San Pedro River near the San Pedro River at Palominas gaging station and near the Lewis Springs DCP stage recorder. The Babocomari River near Tombstone gaging station is downgradient of the major pumping centers. The change in isotopic signature at the Lewis Springs stage recorder could have been the result of alterations in groundwater/surface-water interactions there caused by beaver damming of the river. Base flow in the San Pedro River declined over the periods of record at the three San Pedro River gaging stations in the subwatershed (Palominas, Charleston, and Tombstone), as well as at the Babocomari River near Tombstone gaging station. Precipitation declined slightly from the 1990s to the 2000s, although there is no statistically significant trend in subwatershed precipitation from 1991 to 2012. The occurrence of large winter discharge events appeared to decline and that of large summer discharge events appeared to increase over this same period. Data for physical parameters, general chemistry, nutrient species, select trace elements, and suspended sediment were collected at San Pedro River at Charleston stream-gaging station. These data were summarized over time and analyzed in relation to discharge and season as a means to assess trends over the period of analysis. Federal and State of Arizona drinking-water and human-contact standards were all met and few exceedances occurred for the ecological thresholds investigated. Several constituents showed a significant trend over the period of analysis, but only concentration and flux data for total phosphate, orthophosphate, total nitrogen, suspended sediment, and sulfate were suitable to be used in a weighted regression analysis that statistically accounted for time, discharge, and season. Sulfate concentrations and flux showed a significant downward trend over the period of analysis, whereas total phosphorus and ortho-phosphate showed a relatively small magnitude upward trend relative to standards. Suspended sediment concentrations and flux both showed a significant downward trend in the 1980s, an effect attributed to reduction of cattle in the subwatershed at about this time, and (or) increased cottonwood (Populus fremontii) and willow (Salix goodingii) recruitment, and (or) the curtailment of sand and gravel mining adjacent to the San Pedro River with the designation of the San Pedro Riparian National Conservation Area in 1988. A spike in sediment flux in 2006 may be attributable to the more than 100 debris flows in the Huachuca Mountains during the summer monsoon of that year. Spring discharge along the San Pedro River generally increased at three sites proximate to the Sierra Vista treated effluent recharge facility and varied somewhat with climate at two other sites. Median annual discharge at the recharge facility peaked in 2006, and at Murray Springs and Horsethief Spring, downgradient of the recharge facility, in 2009. Sampling for trace organic compounds in flow from springs was carried out using both discrete sampling and passive sampling methods. Spring samples thus collected showed the presence of trace-organic compounds. Lewis Springs (background site) had the least number of detections, whereas Murray Springs, located directly downgradient of the City of Sierra Vista's treated effluent recharge facility, had the greatest number of detections of all the springs. Discrete samples from the recharge facility had more than twice the detections found in discrete samples from Murray Spring and at much higher concentrations. Few similar trace-organic compounds were detected at both the springs and the treated effluent recharge facility, and the number of detections did not increase during the collection period. Limitations of the study prevented the determination of trace-organic concentration in passive samplers and also prevented linking trace organic compounds detected at the treated effluent recharge facility with compounds detected from the springs. In particular, trace organic compounds could also derive from other sources such as septic systems. Looking at the subwatershed as a whole, base flow was in decline along the entire river reach, but determination of the specific cause of the decline was beyond the scope of this report. Conditions in the area from the municipal pumping center of Sierra Vista and Fort Huachuca northeast to the river (from about the Charleston to Tombstone gaging stations) were more commonly in decline than in regions further south. Both long-term indicators, such as regional aquifer groundwater levels and horizontal gradients, and the isotope analysis indicated that groundwater discharge to the river and thus base flow may continue to decline in that area. South of Charleston, indicators were more mixed. Some indicators in the Hereford reach suggest groundwater discharge to the San Pedro River may be increasing there, whereas some indicators in the Palominas reach suggest groundwater discharge to the river there may be declining.

Study region: The U.S. West Coast, including the Pacific Northwest and California Coastal Basins aquifer systems.Study focus: Groundwater response to interannual to multidecadal climate variability has important implications for security within the water-energy-food nexus. Here we use Singular Spectrum Analysis to quantify the teleconnections between AMO, PDO, ENSO, and PNA and precipitation and groundwater level fluctuations. The computer program DAMP was used to provide insight on the influence of soil texture, depth to water, and mean and period of a surface infiltration flux on the damping of climate signals in the vadose zone.New hydrological insights for the region: We find that PDO, ENSO, and PNA have significant influence on precipitation and groundwater fluctuations across a north-south gradient of the West Coast, but the lower frequency climate modes (PDO) have a greater influence on hydrologic patterns than higher frequency climate modes (ENSO and PNA). Low frequency signals tend to be preserved better in groundwater fluctuations than high frequency signals, which is a function of the degree of damping of surface variable fluxes related to soil texture, depth to water, mean and period of the infiltration flux. The teleconnection patterns that exist in surface hydrologic processes are not necessarily the same as those preserved in subsurface processes, which are affected by damping of some climate variability signals within infiltrating water. (C) 2015 The Authors. Published by Elsevier B.V.