Modeling 21st Century Peak Flows in the Nooksack River Basin in Northwestern Washington State Using Dynamically-downscaled Global Climate Model Projections PDF Download

Author: Evan A. Paul
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ISBN:
Category : Climatic changes
Languages : en
Pages : 0

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The Nooksack River in northwest Washington State provides freshwater for agriculture, municipal, and industrial use and serves as a vital habitat for endangered salmon, a resource that is of cultural and economic importance to the Nooksack Indian Tribe and the surrounding region. Due to the complex topography in the basin and the mild maritime climate of the Puget Sound region, streamflow in the Nooksack River is highly sensitive to fluctuations in air temperature. Global climate models (GCMs) project an increase in air temperatures for the Puget Sound region, and previous modeling within the Nooksack basin projects a reduction in snowpack extent through the 21st century and an increase in winter streamflow magnitude. As more landscape becomes exposed to rain rather than snow and heavy winter precipitation events intensify, peak flows and sediment delivery to streams will likely increase due to rapid runoff, resulting in salmon habitat degradation and increased flood risk. Thus, anticipating the effect of climate change on peak flows is crucial for salmon habitat restoration efforts and flood mitigation planning. To quantify the timing and magnitude of future peak flows, I use a calibrated Distributed Hydrology Soil Vegetation Model (DHSVM) and meteorological forcings from an ensemble of high-emission GCMs dynamically-downscaled using the Weather Research and Forecasting (WRF) model. Due to the variability of climate scenarios depicted by GCMs, a range of streamflow and snowpack magnitude changes in the Nooksack River basin are projected by the hydrology simulations. By the end of the 21st century, results indicate a decrease in annual peak snow-water equivalent (-72% to -82%), a shift in the timing of peak snow-water equivalent to approximately one month earlier, an increase in winter flows (+31% to +56%), a decrease in summer flows (-37% to -72%), and the disappearance of the snowmelt derived spring peak in the hydrograph as the basin transitions from transient to rain-dominant. These results are consistent with previous modeling in the Nooksack River basin and other regional climate change studies in the Pacific Northwest and Puget Sound region. Due to more precipitation falling as rain rather than snow and heavy rain events becoming more frequent and intense, future peak flows are projected to increase in magnitude by 34-60% across all flow durations and return periods that were analyzed, with the largest changes occurring in the high relief subbasins. The frequency of high magnitude, flood-inducing peak flows will also increase into the future, lengthening the flood season by approximately three months.

Author: Susan E. Dickerson
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ISBN:
Category : Climatic changes
Languages : en
Pages : 0

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The Nooksack River has its headwaters in the North Cascade Mountains and drains an approximately 2300 km2 watershed in northwestern Washington State. The timing and magnitude of streamflow in a high relief, snow-dominated drainage basin such as the Nooksack River basin is strongly influenced by temperature and precipitation. Forecasts of future climate made by general circulation models (GCMs) predict increases in temperature and variable changes to precipitation in western Washington, which will affect streamflow, snowpack, and glaciers in the Nooksack River basin. Anticipating the response of the river to climate change is crucial for water resources planning because municipalities, tribes, and industry depend on the river for water use and for fish habitat. I combined modeled climate forecasts and the Distributed-Hydrology-Soil-Vegetation Model (DHSVM) to simulate future changes to timing and magnitude of streamflow in the higher elevations of the Nooksack River, east of the confluence near Deming, Washington. The DHSVM is a physically based, spatially distributed hydrology model that simulates a water and energy balance at the pixel scale of a digital elevation model. I used recent meteorological and landcover data to calibrate and validate the DHSVM. Coarse-resolution GCM forecasts were downscaled to the Nooksack basin following the methods of previous regional studies (e.g., Palmer, 2007) for use as local-scale meteorological input to the calibrated DHSVM. Simulations of future streamflow and snowpack in the Nooksack River basin predict a range of magnitudes, which reflects the variable predictions of the climate change forecasts and local natural variability. Simulation results forecast increased winter flows, decreased summer flows, decreased snowpack, and a shift in timing of the spring melt peak and maximum snow water equivalent. Modeling results for future peak flow events indicate an increase in both the frequency and magnitudes of floods, but uncertainties are high for modeling the absolute magnitudes of peak flows. These results are consistent with previous regional studies which document that temperature-related effects on precipitation and melting are driving changes to snow-melt dominated basins (e.g., Hamlet et al., 2005; Mote et al., 2005; Mote et al., 2008; Adam et al., 2009).

Author: Stephanie E. Truitt
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Category : Climatic changes
Languages : en
Pages : 0

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Stream temperatures in mountain streams in the western Cascade Mountains are heavily influenced by factors such as discharge, air temperature, and as in the case of the Nooksack River Basin in northwest Washington State; snow and glacial melt. The Nooksack basin is sensitive to warming climates due to the regions moderate Pacific maritime climate. Previous modeling studies in the upper Nooksack basins indicate a reduction in snowpack and spring runoff, and a recession of glaciers into the 21st century due to global climate change. How stream temperatures will respond to these changes is unknown. We use the Distributed Hydrology Soil Vegetation Model (DHSVM) coupled with a glacier dynamics model to simulate hydrology and the River Basin Model (RBM) to model stream temperature from present to the year 2090 in the North, Middle, and South forks of the Nooksack River basin. We simulate forecasted climate change effects on hydrology and stream temperature using gridded daily statically downscaled data from 10 global climate models (GCMs) of the Coupled Model Intercomparison Project Phase Five (CMIP5) with two different representative concentration pathways (RCP) RCP4.5 and RCP8.5. Simulation results project a trending increase in stream temperature into the 21st century in all three forks of the Nooksack. There is a strong correlation between rising stream temperatures and warming air temperatures, decreasing stream discharge; and snow and glacial meltwater. We find that the highest stream temperatures and the greatest monthly mean 7-day average of the daily maximum stream temperature (7-DADMax) values are predicted in the lower relief, unglaciated South Fork basin. For the 30 years surrounding the 2075 time period, the mouth of the South Fork is forecasted to have a mean of 115 days above the 16 °C 7-day average of the daily maximum stream temperature threshold. Streams in the Middle and North fork basins with higher elevations that sustain more snow and glacier ice are slower to respond to warming climates due to meltwater contributions, especially in the next 50 years. Towards the end of this century, when snowpack and glacial volume is greatly decreased, the buffering effect of meltwater declines, and the North and Middle forks experience larger increases in mean daily stream temperature. For the 30 years surrounding the 2075 time period, the mouths of the Middle and North forks are forecasted to have means of 35 and 23 days, respectively, above the 16 °C 7-DADMax threshold.

Author: Ryan D. Murphy
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Category : Glaciers
Languages : en
Pages : 0

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Like many watersheds in the North Cascades range of Washington State, USA, streamflow in the Nooksack River is strongly influenced by precipitation and snowmelt in the spring and glacial ice melt in the warmer summer months. With a maritime climate and high relief containing approximately 34km2 of glacial ice, the streamflow response in the Nooksack River basin is sensitive to increases in temperature. Climate projections from global climate models (GCMs) for the 21st Century indicate increases in temperature with variable changes to precipitation. The watershed is a valuable freshwater resource for regional municipalities, industry, and agriculture, and provides critical habitat for endangered salmon species. Thus, understanding the impacts of forecasted climate change is critical for water resources planning purposes. I apply publically available statistically derived 1/16 degree gridded surface climate data along with the Distributed Hydrology Soil Vegetation Model (DHSVM) with newly developed coupled dynamic glacier model to simulate hydrologic and glacial processes through the end of the 21st Century. Simulation results project median winter streamflows to more than double by 2075 due to more precipitation falling as rain rather than snow, and median summer flows to decrease by more than half with a general shift in peak snowmelt derived spring flows toward earlier in the spring. Glaciers are projected to retreat significantly with smaller glaciers disappearing entirely. Ice melt contribution to streamflow is likely to play an important role in sustaining summer baseflows in the Nooksack River. Glacier melt derived streamflow is projected to increase throughout the first half of the 21st century and decrease in the latter half after glacier ice volume decreases substantially.

Author: Kevin Knapp
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ISBN:
Category : Climatic changes
Languages : en
Pages : 0

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The Nooksack River in Whatcom County, Washington is an essential fresh water resource for industry, agriculture, municipalities and serves as vital fish habitat. Like many mountainous watersheds in the western Cascades, the Nooksack Basin is susceptible to shallow mass wasting and debris flows because of its steep slopes, young glaciated terrain, and storms with high intensity precipitation. Understanding how projected reductions in snowpack and increased winter rainfall will affect mass - wasting susceptibility in the Nooksack basin is important, because sediment produced mass wasting will jeopardize valuable aquatic and fish habitat, increase flooding risk in the Nooksack River, and affect estuarine and coastal dynamics. With a projected 60% decrease in snow pack and increase in the snowline elevation by the 2075 climate normal, there will be an increase in exposed forest roads, harvestable forest areas, and previously mapped landslides, which are all documented to increase sediment delivery to streams. Retreating glaciers will produce at least 2 km 2 of exposed moraines, which have the potential to erode, fail and provide additional sediment to streams, especially during large storm events coinciding with minimum snowpack during the fall and early spring seasons . I applied a static infinite - slope ArcGIS model and a dynamic, probabilistic mass - wasting model integrated into the Distributed Hydrology Soil Vegetation Model (DHSVM) to the Nooksack River watershed to determine areas susceptible to mass wasting into the 21 st century. Susceptibility maps produced by the models indicate an increase in regions susceptible to slope failure during the winter months in snow free areas at higher elevations later in the 21 st century. Slope failure susceptibility increased with soil saturation, which is anticipated with higher intense winter rainfall events. Slopes greater than about 30° with thick regolith deposits and lower soil mechanical strength, e.g., sand, loamy sand, sandy loam, silt, moraines, glacial outwash and former landslide deposits were correlated with higher mass - wasting susceptibility. The simpler static ArcGIS infinite - slope model yielded comparable results to the more complex probabilistic method integrated into the DHSVM for identifying areas susceptible to mass wasting.

Author: Emily Esther Gebheim Smoot
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ISBN:
Category : Chinook salmon
Languages : en
Pages : 0

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The Stillaguamish River is a snow-and-rain mixed basin and the fifth largest river in the Puget Sound basin. Elevations in the 1700 km2 Stillaguamish River basin reach roughly 2000 m and historically a snowpack is sustained above 1000 m. Snowmelt in the basin is important for sustaining spring and summer streamflow and buffering stream temperatures. Stream temperature increases are of significant concern because of the threatened Chinook salmon (Oncorhynchus tshawytscha) population. I reexamined projected stream temperatures in the Stillaguamish River by forcing the coupled Distributed Hydrology Soil Vegetation Model and River Basin Model with dynamically downscaled meteorological forcings from the Weather Research and Forecasting model and projected changes in the entire basin, including the Pilchuck subbasin and mainstem through 2099 by applying 12 dynamically downscaled Global Climate Models with high emission scenarios of RCP 8.5. Using an updated version of the River Basin Model, I applied tributary specific calibration parameters and calibrated modeled streamflow and temperature using historical gauges and field measurements. My model calibrations and projections are consistent with other modeling studies in the Stillaguamish and other western Cascade watersheds. Snow covered area in the basin is projected to decrease by 74%, and summer streamflow decreases for the primary locations and at-risk tributaries are projected to be 48% and 53%, respectively for July and August at the end of the century. With the decreases in snowpack and streamflow, stream temperatures reach their peak earlier in the year, in July instead of August which was historically the warmest month. Stream temperatures are projected to increase by 14% on average for the larger primary reaches and 21% for the smaller at-risk tributaries by the 2080s for July and August. The greatest stream temperature increases are in mountainous reaches due to a reduced snowpack. The warmest stream temperatures are projected to occur in late summer along the mainstem of the Stillaguamish River. By the end of the century, six of nine locations examined will exceed the seven-day average daily maximum adult Chinook salmon lethality threshold (22.0 °C). These results indicate that continued work on climate adaptation actions and research will be required to improve Chinook salmon resiliency in the Stillaguamish River as the climate warms.

Author: Katherine Mary Clarke
Publisher:
ISBN:
Category : Salmonidae
Languages : en
Pages : 132

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The Stillaguamish River in northwest Washington State is an important regional water resource for local agriculture, industry, and First Nations tribes and a critical habitat for several threatened and endangered salmonid species, including the Chinook salmon. The river is currently subject to a temperature total maximum daily load, so it is important to understand how projected climate change will affect future stream temperatures and thus salmon populations. Snowpack is the main contributor to spring and summer streamflow and helps to mitigate stream temperatures as air temperatures rise through the summer in the South Fork of the Stillaguamish River. I used gridded historical meteorological data to calibrate the physically-based Distributed Hydrology Soil Vegetation Model and River Basin Model and then applied downscaled, gridded projected climate data to predict how a changing climate will influence hydrology and stream temperature in the South Fork basin through the end of the 21st century.

Author:
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Category :
Languages : en
Pages :

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The ability of water managers to maintain adequate supplies in coming decades depends, in part, on future weather conditions, as climate change has the potential to alter river flows from their current values, possibly rendering them unable to meet demand. Reliable climate projections are therefore critical to predicting the future water supply for the United States. These projections cannot be provided solely by global climate models (GCMs), however, as their resolution is too coarse to resolve the small-scale climate changes that can affect hydrology, and hence water supply, at regional to local scales. A process is needed to 'downscale' the GCM results to the smaller scales and feed this into a surface hydrology model to help determine the ability of rivers to provide adequate flow to meet future needs. We apply a statistical downscaling to GCM projections of precipitation and temperature through the use of a scaling method. This technique involves the correction of the cumulative distribution functions (CDFs) of the GCM-derived temperature and precipitation results for the 20{sup th} century, and the application of the same correction to 21{sup st} century GCM projections. This is done for three meteorological stations located within the Coosa River basin in northern Georgia, and is used to calculate future river flow statistics for the upper Coosa River. Results are compared to the historical Coosa River flow upstream from Georgia Power Company's Hammond coal-fired power plant and to flows calculated with the original, unscaled GCM results to determine the impact of potential changes in meteorology on future flows.

Author: Sabin Shrestha (Civil engineer)
Publisher:
ISBN:
Category : Climatic changes
Languages : en
Pages : 148

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There is a widespread concern that climate change will lead to an increased frequency and intensity of extreme weather events in the 21st century. It is essential, from a watershed management point of view to understand how these alterations in the hydrologic regime would affect the existing water resources. This research, therefore, provides an overview of the hydrologic impacts on the Great Miami River Watershed in Ohio, USA due to projected climatic changes on both low flows and high flows. An extensively used hydrological model, the Soil and Water Assessment Tool (SWAT) was to evaluate the hydrological impacts of climate change. The multi-site model calibration and validation were performed using the SUFI-2 algorithm within SWAT-CUP. The model was calibrated (2005 - 2014) and validated (1995 - 2004) for monthly stream flows at the outlet resulting in Nash - Sutcliffe Coefficients of 0.86 and 0.83, respectively. An ensemble of ten downscaled and bias-corrected climate models from Fifth Phase Coupled Model Intercomparison Project (CMIP5) under two Representative Concentration Pathways(RCPs) 4.5 and 8.5 were used to generate a probable set of climate data (precipitation and temperature). The climate data were then fed into the SWAT model and hydrological changes in the stream in terms of daily discharge were produced for three time-frames: (2016 - 2043) as 2035s, (2044 - 2071) as 2055s, and (2072 - 99) as 2085s and compared against the baseline period (1988 - 2015). The findings from this research showed that low flows using both hydrological and biological indices would increase more than 100% in 2035s but eventually decrease slightly in the later part of the century (2085s). However, the Max Planck Institute Earth System Model (MPI-ESM-LR) used in this study predicted that the biological indices iv under RCP 8.5 would increase slightly at the beginning but decrease considerably in the middle and later part of the century. Analysis showed that the variability of the average 7-day low flows in each year would increase considerably for both emission scenarios. Furthermore, 75th percentile exceedance frequency of monthly low flows was found higher in September, October, and November during the study period. As for high flow analysis, the hydrological index for high flows (7Q10) from an ensemble of 10 climate models predicted to decrease consistently in future. When the results from the two RCPs are compared, high flows would decrease maximum by 22% in 2055s under RCP 8.5 and 21% in 2085s under RCP 4.5. However, the MIROC5 model in RCP 4.5 showed 1.2% increase in 7Q10 high flows during 2035s. The frequency of the 75th percentile non-exceedance flows was also projected to increase in the future. Under the RCP 4.5, the frequency becomes higher in 2055s whereas under the RCP 8.5 most frequent 75th percentile flow would occur in 2085s. Meanwhile, on a monthly scale, the peak would increase more on every month except January and December than that of historical records. The variability of peak discharge was also expected to increase in every other month in both scenarios. The peak would increase considerably especially in August, September, and October when compared to historical months, indicating relatively wetter months in the future years. Finally, this study has demonstrated the effects of changing climates projected by the climate models on extreme flow condition in the large agricultural watershed. The next step of the research will focus on further bias correction on simulated climate data and analysis for future.

Author: Allison Marshall Inouye
Publisher:
ISBN:
Category : Hydrologic models
Languages : en
Pages : 73

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In the Western United States where 50-70% of annual precipitation comes in the form of winter snowfall, water supplies may be particularly sensitive to a warming climate. We worked with a network of stakeholders in the Big Wood Basin, Idaho, to explore how climate change may affect water resources and identify strategies that may help mitigate the impacts. The 8,300 square kilometer region in central Idaho contains a mixture of public and private land ownership, a diversity of landcover ranging from steep forested headwaters to expansive desert shrublands to a concentrated area of urban development that has experienced a quadrupling of population since the 1970s. With nearly 60% of precipitation falling as winter snow, stakeholders expressed concern regarding the vulnerability of the quantity and timing of seasonal snowpack as well as surface water supplies used primarily for agricultural irrigation under projected climate change. Here, we achieve two objectives. The first is the development of a hydrologic model to represent the dynamics of the surface water system in the Big Wood Basin. We use the semi-distributed model Envision-Flow to represent surface water hydrology, reservoir operations, and agricultural irrigation. We calibrated the model using a multi-criteria objective function that considered three metrics related to streamflow and one metric related to snow water equivalent. The model achieved higher an efficiency of 0.74 for the main stem of the Big Wood River and 0.50 for the Camas Creek tributary during the validation period. The second objective is an analysis of the Big Wood Basin hydrology under alternative future climate scenarios. We forced the calibrated model with three downscaled CMIP5 climate model inputs representing a range of possible future conditions over the period 2010-2070. The climate models simulate an increase in basin average annual air temperature ranging from 1.6-5.7oC in the 2060s compared to the 1980-2009 average. The climate models show less of a clear trend regarding precipitation but in general, one model simulates precipitation patterns similar to historic, one is slightly wetter than historic, and one is slightly drier than historic by the mid-21st century. Under these future climate scenarios, the depth of April 1 SWE may decline by as much as 92% in the 2060s compared to the historic average. Mid to high elevations exhibit the largest reductions in SWE. Simulated streamflows show a shift in timing, with peak flows occurring up to three weeks earlier and center of timing from two to seven weeks earlier in the 2050-2069 period compared to the historic period. Reduced peak flows of 14-70% were simulated by mid-century. The simulated total annual streamflow, though, fell within the historic interquartile range for most years in the future period. These and other metrics considered suggest that the surface water hydrology of the Big Wood Basin is likely to be impacted by climate change. If the natural water storage provided by the annual snowpack is reduced and timing of streamflows shifts, water resource use and management may need to change in the future. This work provides a foundation from which to explore alternative management scenarios. The approach used here can be transferred to other watersheds to further assess how water resources may be affected by climate change.