An official website of the United States government
Abstract Arctic hydrology is experiencing rapid changes including earlier snow melt, permafrost degradation, increasing active layer depth, and reduced river ice, all of which are expected to lead to changes in stream flow regimes. Recently, long-term (>60 years) climate reanalysis and river discharge observation data have become available. We utilized these data to assess long-term changes in discharge and their hydroclimatic drivers. River discharge during the cold season (October–April) increased by 10% per decade. The most widespread discharge increase occurred in April (15% per decade), the month of ice break-up for the majority of basins. In October, when river ice formation generally begins, average monthly discharge increased by 7% per decade. Long-term air temperature increases in October and April increased the number of days above freezing (+1.1 d per decade) resulting in increased snow ablation (20% per decade) and decreased snow water equivalent (−12% per decade). Compared to the historical period (1960–1989), mean April and October air temperature in the recent period (1990–2019) have greater correlation with monthly discharge from 0.33 to 0.68 and 0.0–0.48, respectively. This indicates that the recent increases in air temperature are directly related to these discharge changes. Ubiquitous increases in cold and shoulder-season discharge demonstrate the scale at which hydrologic and biogeochemical fluxes are being altered in the Arctic.
more »
« less
Warming of the Willamette River, 1850–present: the effects of climate change and river system alterations
Abstract. Using archival research methods, we recovered and combined data from multiple sources to produce a unique, 140-year record of daily watertemperature (Tw) in the lower Willamette River, Oregon (1881–1890, 1941–present). Additional daily weather and river flow records from the 1850s onwards are used to develop and validate a statistical regression model of Tw for 1850–2020. The model simulates the time-lagged response of Tw to air temperature and river flow and is calibrated for three distinct time periods: the late 19th, mid-20th, and early 21st centuries. Results show that Tw has trended upwards at 1.1 ∘C per century since the mid-19th century, with the largest shift in January and February (1.3 ∘C per century) and the smallest in May and June (∼ 0.8 ∘C per century). The duration that the river exceeds the ecologically important threshold of 20 ∘C has increased by about 20 d since the 1800s, to about 60 d yr−1. Moreover, cold-water days below 2 ∘C have virtually disappeared, and the river no longer freezes. Since 1900, changes are primarily correlated with increasesin air temperature (Tw increase of 0.81 ± 0.25 ∘C) but also occur due to alterations in the river system such as depth increases from reservoirs (0.34 ± 0.12 ∘C). Managed release of water affects Tw seasonally, with an average reduction of up to 0.56 ∘C estimated for September. River system changes have decreased variability (σ) in daily minimum Tw by 0.44 ∘C, increased thermal memory, reduced interannual variability, and reduced the response to short-term meteorological forcing (e.g., heat waves). These changes fundamentally alter the response of Tw to climate change, posing additional stressors on fauna.
more »
« less
- Award ID(s):
- 2013280
- PAR ID:
- 10546565
- Publisher / Repository:
- European Geophysical Union
- Date Published:
- Journal Name:
- Hydrology and Earth System Sciences
- Volume:
- 27
- Issue:
- 14
- ISSN:
- 1607-7938
- Page Range / eLocation ID:
- 2807 to 2826
- Subject(s) / Keyword(s):
- climate change, water temperature, anthropogenic change
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract The Mississippi River is a vital economic corridor used for generating hydroelectric power, transporting agricultural products, and municipal and industrial water use. Communities, industries, and infrastructure along the Mississippi River face an uncertain future as it grows more susceptible to climate extremes. A key challenge is determining whether Mississippi river discharge will increase or decrease during the 21st century. Because the 20th century record is limited in time, paleoclimate data and model simulations provide enhanced understanding of the basin's hydroclimate response to external forcing. Here, we investigate how anthropogenic forcing in the 20th century shifts the statistics of river discharge compared to a Last Millennium (LM) baseline using simulations from the Community Earth System Model Last Millennium Ensemble. We present evidence that the 20th century exhibits wetter conditions (i.e., increased river discharge) over the basin compared to the pre‐industrial, and that land use/land cover changes have a significant control on the hydroclimatic response. Conversely, while precipitation is projected to increase in the 21st century, the basin is generally drier (i.e., decreased river discharge) compared to the 20th century. Overall, we find that changes in greenhouse gases contribute to a lower risk of extreme discharge and flooding in the basin during the 20th century, while land use changes contribute to increased risk of flooding. The additional climate information afforded by the LM simulations offers an improved understanding of what drove extreme flooding events in the past, which can help inform the development of future regional flood mitigation strategies.more » « less
-
Widespread salinization—and, in a broader sense, an increase in all total dissolved solids (TDS)—is threatening freshwater ecosystems and the services they provide (e.g., drinking water provision). We used a mixed modeling approach to characterize long-term (2010–2018) spatio-temporal variability in TDS within the Monongahela River basin and used this information to assess the extent and drivers of vulnerability. The West Fork River was predicted to exceed 500 mg/L a total of 133 days. Occurrence and duration (maximum = 28 days) of—and thus vulnerability to—exceedances within the West Fork River were driven by low flows. Projected decreases in mean daily discharge by ≤10 cfs resulted in an additional 34 days exceeding 500 mg/L. Consistently low TDS within the Tygart Valley and Cheat Rivers reduced vulnerability of the receiving Monongahela River to elevated TDS which was neither observed (maximum = 419 mg/L) nor predicted (341 mg/L) to exceed the secondary drinking water standard of 500 mg/L. Potential changes in future land use and/or severity of low-flow conditions could increase vulnerability of the Monongahela River to elevated TDS. Management should include efforts to increase assimilative capacity by identifying and decreasing sources of TDS. Upstream reservoirs could be managed toward low-flow thresholds; however, further study is needed to ensure all authorized reservoir purposes could be maintained.more » « less
-
Abstract The Colorado River Basin is a hydrologic river network that directs runoff from rain and snow falling on mountains, primarily in Colorado and Wyoming, to the Colorado River Delta in Mexico. Over the last century, in response to basin‐wide water shortages, legal agreements between stakeholders in seven U.S. states and Mexico, hydrologic flows from users on the main stem of the river have been reallocated to junior water rights holders. Municipalities, businesses, farmers, and households utilize the Colorado River water to produce and trade valuable, water‐derived goods and services, which effectively reallocates water through a continually adapting, boundary‐free economic river network providing indirect access to virtual Colorado River water. We conceptualize the Colorado River Basin as a multiplex network comprised of interdependent natural flow networks, direct (infrastructural) flow networks, and indirect (virtual) flow networks. Using this reframing, we quantify the total hydrosocial impact of the Drought Contingency Plan (DCP) on Lower Basin states. For each Mm3of water reduced through the DCP, Arizona, Nevada, and California lose an additional 0.42–0.43 Mm3, 0.33–0.51 Mm3, and 1.06–1.10 Mm3of virtual water flow, respectively. Hence, the DCP will require Arizona, Nevada, and Southern California to restructure how they use water, relying less on direct and indirect consumption of the Colorado River water and finding more indirect water sources outside that basin.more » « less
-
Abstract Understanding drivers of river mobility—temporal shifts in river channel positions—is critical for managing fluvial landscapes sustainably and for interpreting past river responses to climate change. However, direct observations linking river mobility and water discharge variability are scarce. Here, we pair multi‐annual measurements of daily water discharge and river mobility, estimated from Landsat, for 48 rivers worldwide. We show that, across climates and planforms, river mobility is correlated with water discharge variability over daily, intra‐annual, and inter‐annual timescales. For similar mean discharge, higher discharge variability is associated with up to an order‐of‐magnitude faster floodplain reworking. A random forest regression model indicates that discharge variability is the primary predictor of river mobility, when compared to mean water discharge, sediment concentration, and channel‐bed slope. Our results suggest that enhanced hydro‐climatic extremes could accelerate future river mobility, and that past changes to discharge variability may explain the fabric of fluvial strata.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.5194/hess-27-2807-2023
