Analyzing the Impacts of Serial Correlation and Shift on the Streamflow Variability within the Climate Regions of Contiguous United States (original) (raw)
Related papers
Hydrology, 2016
The study focused on investigating the presence of change patterns in 600 unimpaired streamflow stations across the continental U.S. at different time intervals to understand the change patterns that can provide significant insight regarding climate variability and change. Each station had continuous streamflow data of at least 30 years (the entire dataset covered a range of 109 years). Presence of trends and shifts were detected in water year and the four seasons (fall, winter, spring, and summer) analyzing the water year and seasonal mean flows. Two non-parametric tests, namely, the Mann-Kendall test and the Pettitt's test were used to identify the trends and the shifts, respectively. The results showed an increasing trend in the northeast and upper-mid regions, whereas southeast and northwest regions underwent a decrease. Shifts followed similar patterns as trends with higher number of stations with significant change. Fall and spring showed the highest number of stations with increasing and decreasing change, respectively, in the seasonal analyses. Results of this study may assist water managers to understand the streamflow change patterns across the continental U.S., especially at the regional scale since this study covers a long range of years with a large number of stations in each region.
An Analysis of Streamflow Trends in the Southern and Southeastern US from 1950–2015
Water, 2020
In this article, the mean daily streamflow at 139 streamflow-gaging stations (sites) in the southern and southeastern United States are analyzed for spatial and temporal patterns. One hundred and thirty-nine individual time-series of mean daily streamflow were reduced to five aggregated time series of Z scores for clusters of sites with similar temporal variability. These aggregated time-series correlated significantly with a time-series of several climate indices for the period 1950–2015. The mean daily streamflow data were subset into six time periods—starting in 1950, 1960, 1970, 1980, 1990, and 2000, and each ending in 2015, to determine how streamflow trends at individual sites acted over time. During the period 1950–2015, mean monthly and seasonal streamflow decreased at many sites based on results from traditional Mann–Kendall trend analyses, as well as results from a new analysis (Quantile-Kendall) that summarizes trends across the full range of streamflows. A trend departur...
The regional persistence and variability of annual streamflow in the United States
Water Resources Research, 1998
Inference from individual streamflow records can be extremely misleading, even for large samples. One is often tempted to trust information available from a streamflow record rather than to exploit regional average statistics of those records. This study documents that regional average streamflow statistics usually contain much more information about the variability and persistence of streamflow at a particular site than does the individual streamflow record for that site. Experiments are performed using time series of annual streamflow at 1544 gauging stations across the continental United States. We document that 18 broad water resource regions of the United States are homogeneous in terms of the year-to-year persistence of streamflow, whereas much smaller regions are required to obtain homogeneity in terms of the variability of streamflow. Classical homogeneity measures ignore the serial correlation of streamflow. Instead, homogeneity is quantified using the sampling properties of at-site estimates of the coefficient of variation C v and lag-one correlation 1 of annual streamflows. Additional experiments using the Hurst coefficient reveal that the long-term persistence structure of historical annual streamflow series is indistinguishable from the long-term persistence structure of either an AR(1) or ARMA(1,1) process. If historical flow series are generated from either an AR(1) or ARMA(1,1) process, then even given 1544 observed time series, we are unable to distinguish between those two processes.
Climate elasticity of streamflow in the United States
Water Resources Research, 2001
Precipitation elasticity of streamflow, e•,, provides a measure of the sensitivity of streamflow to changes in rainfall. Watershed model-based estimates of e•, are shown to be highly sensitive to model structure and calibration error. A Monte Carlo experiment compares a nonparametric estimator of e•, with various watershed model-based approaches. The nonparametric estimator is found to have low bias and is as robust as or more robust than alternate model-based approaches. The nonparametric estimator is used to construct a map of e•, for the United States. Comparisons with 10 detailed climate change studies reveal that the contour map of e•, introduced here provides a validation metric for past and future climate change investigations in the United States. Further investigations reveal that e•, tends to be low for basins with significant snow accumulation and for basins whose moisture and energy inputs are seasonally in phase with one another. The Budyko hypothesis can only explain variations in e•, for very humid basins.
Journal of Hydrology, 2004
A new method for frequency analysis of hydrologic time series was developed to facilitate the estimation and reconstruction of individual or groups of frequencies from hydrologic time-series and facilitate the comparison of these isolated time-series components across data types, between different hydrologic settings within a watershed, between watersheds, and across frequencies. While climate-related variations in inflow to and outflow from aquifers have often been neglected, the development and management of ground-water and surface-water resources has required the inclusion of the assessment of the effects of climatic variability on the supply and demand and sustainability of use. The regional assessment of climatic variability of surface-water and ground-water flow throughout the southwestern United States required this new systematic method of hydrologic time-series analysis.
2021
Design floods serve an important role in environmental planning and management; however, flood frequency analyses often assume that historical records are stationary despite anthropogenic changes across the watershed. Such changes are especially prevalent in the southeastern United States where rapid population growth coupled with climate change is dramatically altering catchment response. To understand how design floods have changed over time, this study investigates historical records of daily river discharge at over 5,800 USGS gauges in the Southeastern USA. When looking at trends in daily discharges, we find that 40% experienced a significant (p<0.05) increase in daily discharge, 50% experienced significant decrease, and 10% experienced no significant change in daily discharge. We observe that, in general, gages exhibiting increasing daily discharge are spatially concentrated east of the Appalachian Mountains and gages exhibiting decreasing daily discharge are spatially conce...
Journal of Hydrology, 2009
The study presented here utilized long-term streamflow records (over 500 years) to investigate the influence of interannual/interdecadal climate variability on the Colorado River basin. 19 unimpaired water year streamflow stations were reconstructed utilizing partial least square regression using standard tree ring chronologies. The spatial and temporal variability of drought was evaluated for all the stations for the different centuries in the record. Finally, the relationship between individual impact of ENSO, PDO, and AMO and its combined effect on streamflow was determined using the non parametric Rank Sum test for different lag years (0, +1, +2, and +3) of streamflow. This research also determined the change in streamflow volume with respect to the long-term mean volume of the basin due to individual and coupled effect of oceanic climate influences. Results indicate that there is an increase in streamflow during El Niño and decreased streamflow during La Niña in the basin. Similarly, PDO warm/cold resulted in increased/decreased streamflow. There were few stations related to the AMO in the basin. Finally, the differences in the Upper and Lower basin were noted in the magnitude of changes in streamflow (in terms of percentage) under different individual and coupled influences of ENSO, PDO, and AMO.
Structure and Detectability of Trends in Hydrological Measures over the Western United States
Journal of Hydrometeorology, 2009
This study examines the geographic structure of observed trends in key hydrologically relevant variables across the western United States at 1 /88 spatial resolution during the period 1950-99. Geographical regions, latitude bands, and elevation classes where these trends are statistically significantly different from trends associated with natural climate variations are identified. Variables analyzed include late-winter and spring temperature, winter-total snowy days as a fraction of winter-total wet days, 1 April snow water equivalent (SWE) as a fraction of October-March (ONDJFM) precipitation total [precip(ONDJFM)], and seasonal [JFM] accumulated runoff as a fraction of water-year accumulated runoff. Observed changes were compared to natural internal climate variability simulated by an 850-yr control run of the finite volume version of the Community Climate System Model, version 3 (CCSM3-FV), statistically downscaled to a 1 /88 grid using the method of constructed analogs. Both observed and downscaled model temperature and precipitation data were then used to drive the Variable Infiltration Capacity (VIC) hydrological model to obtain the hydrological variables analyzed in this study. Large trends (magnitudes found less than 5% of the time in the long control run) are common in the observations and occupy a substantial part (37%-42%) of the mountainous western United States. These trends are strongly related to the large-scale warming that appears over 89% of the domain. The strongest changes in the hydrologic variables, unlikely to be associated with natural variability alone, have occurred at medium elevations [750-2500 m for JFM runoff fractions and 500-3000 m for SWE/Precip(ONDJFM)] where warming has pushed temperatures from slightly below to slightly above freezing. Further analysis using the data on selected catchments indicates that hydroclimatic variables must have changed significantly (at 95% confidence level) over at least 45% of the total catchment area to achieve a detectable trend in measures accumulated to the catchment scale.
Changes in U.S. Streamflow and Western U.S. Snowpack
Journal of Hydrologic Engineering, 2008
Hydroclimatological records are increasingly examined for evidence of trends and shifts that may assist in prediction of future climate change scenarios. This study investigates the trend and step changes in U.S. streamflow over a 52-year period ͑1951-2002͒ using data from 639 unimpaired streamflow stations categorized according to the hydrologic unit codes. This is particularly relevant since the issue of climate change is of interest to many, and studies have indicated an abrupt change in climate around the year 1976/77. Trends were evaluated using three statistical tests: Spearman's rho, Mann-Kendall, and linear regression, and step changes were evaluated using the rank sum and student's t test. The temporal resolution used for the study included water year ͑Oct-Sept͒, autumn-winter ͑Oct-Mar͒, and spring-summer ͑Apr-Sept͒ periods. Additionally, April 1 snow-water equivalent ͑SWE͒ data for 121 SNOTEL stations for the period 1941 to 2004 were used to test for the trends in the western U.S. The multiple statistical tests provided robust results for regions with significant changes. Results indicated that the Mississippi and Missouri regions have an increasing trend in streamflow quantity. The Pacific Northwest and South Atlantic-Gulf regions have streamflow decreasing due to a step change in climate. Decreasing trends for the SWE were noted for a number of stations in the states of Oregon and Utah.