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USGS2010

Estimated Withdrawals and Other Elements of Water Use in the Great Lakes Basin of the United States in 2005

Estimates of water withdrawals in the United States part of the Great Lakes Basin and 107 of its watersheds designated by the 8-digit hydrologic unit code (HUCs) indicate that about 30.3 billion gallons per day (Bgal/d) were withdrawn for practically all categories of use in 2005. Virtually all water withdrawn was freshwater. Surface-water withdrawals totaled 28.8 Bgal/d, or 95 percent of total withdrawals; about 24 Bgal/d was withdrawn from the Great Lakes or their connecting channels. Total withdrawals, and total surface-water withdrawals, decreased 7 percent from 1995 to 2005, generally following the withdrawal trends of industrial use and that of the largest use-thermoelectric power. Groundwater withdrawals increased 3 percent from 1995 to 2005 and 33 percent during 1985-2005. The substantial increase since 1985 results primarily from increases in irrigation and self-supplied domestic withdrawals. In 2005, withdrawals for public supply, domestic, and irrigation use accounted for 81 percent of groundwater withdrawals. About 21.9 Bgal/d, or 72 percent of total withdrawals for 2005, was used for thermoelectric power. Virtually all of this water was derived from surface water and used for once-through cooling at powerplants. As such, the reuse potential of this water in the basin is high, with the majority of the withdrawn water returned to its surface-water source. Public-supply withdrawals were 3.81 Bgal/d (13 percent), with withdrawals declining by about 13 percent from 1995 to 2005. In 2005, about 77 percent of the population in the Great Lakes Basin obtained drinking water from public suppliers, compared to about 78 percent in 1995 and 83 percent in 1985. Surface water consistently provided about 88 percent of the total withdrawals for public supply since 1985. Self-supplied industrial withdrawals in 2005 totaled 2.93 Bgal/d (10 percent), possibly as much as 30 percent less than in 1995. Surface water was the source for 95 percent of industrial withdrawals. Combined withdrawals for mining, irrigation, domestic, aquaculture, and livestock use (in order of decreasing rate) were 1.63 Bgal/d, or only 5 percent of total withdrawals; the withdrawals were distributed almost equally between surface-water and groundwater sources. Withdrawals for each of these uses, except livestock, increased almost continuously during 1985-2005. Withdrawals for mining increased 103 percent and for irrigation 94 percent during 1985-2005; livestock withdrawals decreased 25 percent from their peak in 1990. The number of irrigated acres increased 56 percent since 1985, totaling 750,000 acres in 2005. No use of reclaimed wastewater for industrial or irrigation applications was reported; however, sources of information regarding its use were sparse. Within the basin, the Lake Michigan watershed accounted for 15.0 Bgal/d, or 49 percent, of total water withdrawals for 2005; an estimated 12.3 Bgal/d was withdrawn directly from Lake Michigan. The State of Michigan accounted for 38 percent of total water withdrawals, representing the largest surface-water withdrawals (primarily for thermoelectric power use) and groundwater withdrawals (primarily for public supply and self-supplied domestic use). A disproportionately large percentage of surface-water withdrawals (6 percent, 1.80 Bgal/d) were in Illinois, given this state represents less than 1 percent of the land area of the basin. Ninety percent of the Illinois population served by the water withdrawn from Lake Michigan for public supply resides outside the basin. Within land-based HUCs, the Lower Maumee (04100009) of Ohio accounted for the largest total withdrawal and total surface-water withdrawal (about 0.75 Bgal/d). The St. Joseph (04050001) of Michigan and Indiana accounted for the largest total groundwater withdrawal (0.25 Bgal/d).

Scientific Investigations Report↗

USGS1987

Geohydrologic framework of the coastal plain aquifers of South Carolina

The U.S. Geological Survey is conducting a series of investigations of aquifers throughout the United States as a part of the RASA (Regional Aquifer System Analysis) program. These investigations provide a comprehensive regional understanding of groundwater resources throughout the Nation. The Coastal Plain aquifers in South Carolina are being studied as a part of this program. An important part of a description of the groundwater resources is the development of a geohydrologic framework. Such a framework delineates the aquifers through which groundwater flows and the confining units which retard the flow of groundwater between aquifers. The Coastal Plain of South Carolina is underlain by a wedge of sediments that thickens from its inner margin, the Fall Line, to the coast and consists of sand, silt, clay, and limestone of Late Cretaceous to Holocene age. These sediments are underlain by pre-Cretaceous rocks consisting of consolidated sedimentary rocks of Triassic age and a complex of metamorphic and igneous rocks similar to those found near the surface in the Piedmont province of the State. The geohydrologic framework that divides the sediments of the South Carolina Coastal Plain into the Coastal Plain aquifer system is delineated by eleven geohydrologic sections and four maps showing the configuration of the top or base of individual aquifers. Although flow within the Coastal Plain aquifer system is three dimensional, simplifying the system by dividing it into a framework of discrete hydrologic units can aid significantly in understanding the hydrology of the system. This framework is the basis for the aquifers used in potentiometric mapping, transmissivity mapping, geochemical analysis, and groundwater flow modeling for the South Carolina RASA program. (Lantz-PTT)

South Carolina↗

USGS1995

Validation of national land-cover characteristics data for regional water-quality assessment

Land-cover information is used routinely to support the interpretation of water-quality data. The Prototype 1990 Conterminous US Land Cover Characteristics Data Set, developed primarily from Advanced Very High Resolution Radiometer (AVHRR) data, was made available to the US Geological Survey's National Water-Quality Assessment (NAWQA) Program. The study described in this paper explored the utility of the 1990 national data set for developing quantitative estimates of the areal extent of principal land-cover types within large areal units. Land-cover data were collected in 1993 at 210 sites in the Central Nebraska Basins, one of the NAWQA study units. Median percentage-corn estimates for each sampling stratum wre used to produce areally weighted estimates of the percentage-corn cover for hydrologic units. Comparison of those areal estimates with an independent source of 1992 land-cover data showed good agreement. -Authors

Geocarto International↗

USGS2023

The incredible HALK: borrowing data for age assignment

Understanding age and growth are important for fisheries science and management; however, age data are not routinely collected for many populations. We propose and test a method of borrowing age–length data across increasingly broader spatiotemporal levels to create a hierarchical age–length key (HALK). We assessed this method by comparing growth and mortality metrics to those estimated from lake–year age–length keys ages using seven common freshwater fish species across the upper Midwestern United States. Levels used for data borrowing began most specifically by borrowing within lake across time and increased in breadth to include data within the Hydrologic Unit Code (HUC) 10 watershed, HUC8 watershed, Level III Ecoregion, and finally a species-wide data ALK using all available data with our study for a species. Median deviation in mean length of age-3 fish was within 1 cm for the most specific HALK levels, and median deviation in total annual mortality was close to 0 for most species when borrowing occurred within HUC10 and HUC8 watersheds. Percent error in growth curves increased with data borrowing, but plateaued—or even decreased—for some species when data borrowing expanded across spatial levels. We present the HALK as a method for gaining age information about a fishery when age data are unavailable.

Illinois, Indiana, Iowa, Michigan, Minnesota, Sout↗

USGS1991

Hydrogeology and ground-water flow in the carbonate rocks of the Little Lehigh Creek basin, Lehigh County, Pennsylvania

The Little Lehigh Creek basin is underlain mainly by a complex assemblage of highly-deformed Cambrian and Ordovician carbonate rocks. The Leithsville Formation, Allentown Dolomite, Beekmantown Group, and Jacksonburg Limestone act as a single hydrologic unit. Ground water moves through fractures and other secondary openings and generally is under water-table conditions. Median annual ground-water discharge (base flow) to Little Lehigh Creek near Allentown (station 01451500) during 1946-86 was 12.97 inches or 82 percent of streamflow. Average annual recharge for 1975-83 was 21.75 inches. Groundwater and surface-water divides do not coincide in the basin. Ground-water underflow from the Little Lehigh Creek basin to the Cedar Creek basin in 1987 was 4 inches per year. A double-mass curve analysis of the relation of cumulative precipitation at Allentown to the flow of Schantz Spring for 1956-84 showed that cessation of quarry pumping and development of ground water for public supply in the Schantz Spring basin did not affect the flow of Schantz Spring. Ground-water flow in the Little Lehigh Creek basin was simulated using a finite-difference, two-dimensional computer model. The geologic units in the modeled area were simulated as a single water-table aquifer. The 134-squaremile area of carbonate rocks between the Lehigh River and Sacony Creek was modeled to include the natural hydrologic boundaries of the ground-water-flow system. The ground-water-flow model was calibrated under steady-state conditions using 1975-83 average recharge, evapotranspiration, and pumping rates. Each geologic unit was assigned a different hydraulic conductivity. Initial aquifer hydraulic conductivity was estimated from specific-capacity data. The average (1975-83) water budget for the Little Lehigh Creek basin was simulated. The simulated base flow from the carbonate rocks of the Little Lehigh Creek basin above gaging station 01451500 is 11.85 inches per year. The simulated ground-water underflow from the Little Lehigh Creek basin to the Cedar Creek basin is 4.04 inches per year. For steady-state calibration, the root-mean-squared difference between observed and simulated heads was 21.19 feet. The effects of increased ground-water development on base flow and underflow out of the Little Lehigh Creek basin for average and drought conditions were simulated by locating a hypothetical well field in different parts of the basin. Steady-state simulations were used to represent equilibrium conditions, which would be the maximum expected long-term effect. Increased ground-water development was simulated as hypothetical well fields pumping at the rate of 15, 25, and 45 million gallons per day in addition to existing ground-water withdrawals. Four hypothetical well fields were located near and away from Little Lehigh Creek in upstream and downstream areas. The effects of pumping a well field in different parts of the Little Lehigh Creek basin were compared. Pumping a well field located near the headwaters of Little Lehigh Creek and away from the stream would have greatest effect on inducing underflow from the Sacony Greek basin and the least effect on reducing base flow and underflow to the Ceda^r Creek basin. Pumping a well field located near the headwaters of Little Leh|igh Creek near the stream would have less impact on inducing underflow from|the Sacony Creek basin and a greater impact on reducing the base flow of Little Lehigh Creek because more of the pumpage would come from diverted base flow. Pumping a well field located in the downstream area of the Little Lehigh Creek basin away from the stream would have the greatest effect on the underflow to the Cedar Creek basin. Pumping a well field located in the downstream area of the Little Lehigh Creek basin near the stream would have the greatest effect on reducing the base flow of Little Lehigh Cteek. Model simulations show that groundwater withdrawals do not cause a proportional reduction in base flow. Under average conditions, ground-water withdrawals are equal to 48 to 70 percent of simulated base-flow reductions; under drought conditions, ground-water withdrawals are equal to 35 to 73 percent of simulated base-flow reductions. The hydraulic effects of pumping largely depend on well location. In the Little Lehigh basin, surface-water and ground-water divides do not coincide, and ground-water development, especially near surface-water divides, can cause ground-water divides to shift and induce ground-water underflow from adjacent basins. Large-scale ground-water pumping in a basin may not produce expected reductions of base flow in that basin because of shifts in the ground-water divide; however, such shifts can reduce base flow in adjacent surface-water basins.

Water-Resources Investigations Report↗

USGS1996

Geohydrology, water levels and directions of flow, and occurrence of light-nonaqueous-phase liquids on ground water in northwestern Indiana and the Lake Calumet area of northeastern Illinois

A study was performed by the U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency, to describe the geohydrology and distribution of light-nonaqueousphase liquids in an industrialized area of northwestern Indiana and northeastern Illinois. The geologic units of concern underlying this area are the carbonates of the Niagaran Series, the Detroit River and Traverse Formations; the Antrim Shale; and sands, silts, and clays of Quaternary age. The hydrologic units of concern are surface water, the Calumet aquifer, the confining unit, and the Silurian-Devonian aquifer. Water levels collected in June 1992 indicate that the water-table configuration generally is a subdued reflection of topography. Recharge from landfill leachate and ponded water, discharge to sewers, and pumping also affect the water-table configuration. A depression in the potentiometric surface of the Silurian-Devonian aquifer results from pumping. Light-nonaqueous-phase liquids were detected near petroleum handling, industrial and waste-disposal facilities. Horizontal ground-water velocity at the water table in the confining unit ranged from 4.4x10 -4 to 1.0x10 -3 feet per day. Horizontal ground-water velocity in the Calumet and Silurian-Devonian aquifers ranged from 1.0x10 -2 to 3.4x10 -1 and from 1.4x10 -2 to 2.9x10 -2 feet per day, respectively. Vertical hydraulic gradients indicate generally downward flow from the Calumet aquifer into the confining unit, then into the Silurian-Devonian aquifer. Calculated vertical groundwater velocity through the weathered and unweathered parts of the confining unit are 3.8x10 -2 and 1.5x10 -3 feet per day, respectively.

Illinois, Indiana↗

USGS2018

Estimates of water use and trends in the Colorado River Basin, Southwestern United States, 1985–2010

The Colorado River Basin (CRB) drains 246,000 square miles and includes parts of California, Colorado, Nevada, New Mexico, Utah, and Wyoming, and all of Arizona (Basin States). This report contains water-use estimates by category of use for drainage basins (Hydrologic Unit Code 8; HUC‑8) within the CRB from 1985 to 2010, at 5-year intervals. Estimates for public supply, domestic, commercial, industrial, irrigation, livestock, mining, aquaculture, hydroelectric and thermoelectric power, and wastewater returns are tabulated as (1) water withdrawals from groundwater or surface‑water sources of fresh or saline quality, (2) water delivered for domestic use, (3) wastewater returns and instream use (hydroelectric), and (4) consumptive use, or water that is consumed (USGS definition) and not available for immediate reuse. Water transported outside of the CRB (interbasin transfers) is not included as part of withdrawals and are not accounted for in any category of use within the CRB. Total withdrawals in the CRB (excluding interbasin transfers) averaged about 17 million acre-feet (maf) from 1985 to 2010, peaked at about 17.76 maf in 2000, and reached their lowest levels of 16.43 maf in 1990. Interbasin transfers to serve mostly public-supply and irrigation needs outside of the CRB are reported for 2000, 2005, and 2010 only, and averaged 5.40 maf. More surface water was used in the CRB than groundwater, averaging about 78 percent of total withdrawals, and its use increased less than 2 percent from 1985 to 2010, while groundwater withdrawals decreased about 12 percent. From 1985 to 2010, surface water averaged 98 percent of withdrawals in the upper CRB, and about 59 percent in the lower CRB. Nearly all withdrawals were freshwater, but some saline groundwater was used for mining and self-supplied industrial. Interbasin transfers have a large effect on flows in the Colorado River and are listed in this report separately with no explanation of how the water is used outside of the CRB. There are 34 interbasin transfers that conveyed an estimated 5.83, 5.20, and 5.18 maf out of the CRB in 2000, 2005, and 2010, respectively. The largest interbasin transfers are in the lower CRB and convey surface water (Colorado River water) to southern California; these accounted for 80 to 84 percent of total interbasin transfers in the CRB from 2000 to 2010. Intrabasin transfers are conveyances of surface water that cross drainage basin or State boundaries in the CRB, but the water does not leave the CRB. There are many intrabasin transfers in the CRB, but this report lists 11 that are mostly in the State of Colorado. The largest is the Central Arizona Project (CAP), through which more than 1.00 maf of water was provided to irrigate nearly 1 million acres in Maricopa, Pinal, and Pima Counties, as well as provide municipal water for Phoenix and Tucson, Arizona, during 2000, 2005, and 2010. In 2010, interbasin and intrabasin transfers accounted for 24 and 11 percent of the total water withdrawals in CRB, respectively, with the larger volumes being conveyed out of the lower CRB. Total population in the CRB increased from 4.56 to 9.44 million people from 1985 to 2010. Most of those people were in the lower CRB, with 86 percent of the total in 1985, and 90 percent of the total in 2010. Total public-supply withdrawals in the CRB provided most people with their potable water, and averaged about 1.63 maf from 1985 to 2010, ranging from about 1.07 maf in 1985 to about 2.10 maf in 2010, when it peaked. Most of public-supply withdrawals occurred in the lower CRB, ranging from 87 to 91 percent of total public-supply withdrawals in the CRB over the 25 years. Total domestic use, comprised of public-supply deliveries and self-supply domestic withdrawals, increased more than 90 percent from 1985 to 2010, from about 0.80 maf to about 1.54 maf. Domestic daily per-capita use rates in the CRB ranged from about 144 (1985) to about 121 (2000) gallons (gal) per ‑ capita between 1985 and 2010. When comparing domestic daily per-capita rates for the upper and lower CRB, people in the lower CRB, on average, used less water for domestic purposes at 128 gal per-capita daily (1985–2010), while those in the upper CRB for the same time period averaged 133 gal per-capita daily. The trend in daily per-capita use rates for the entire CRB fluctuated between the reporting years, but decreased overall, indicating that more people used less water in 2010 than in 1985, likely due to improved infrastructure, conservation, and improvements to water using appliances in homes and businesses. Irrigation accounted for most total withdrawals in the CRB, excluding instream use for hydroelectric power and interbasin transfers, averaging 85 percent from 1985 to 2010. Far more surface water than groundwater was used for irrigation in both the upper and lower CRB, but in the upper CRB, it accounted for an average of more than 98 percent of the total withdrawals (1985–2010), whereas in the lower CRB, surface-water withdrawals for irrigation averaged 61 percent of total withdrawals. On average, the upper CRB accounted for 56 percent of total irrigated acres, and the irrigation systems in the upper CRB trended towards more efficient sprinkler systems from 1985 to 2010. Long-term drought in the CRB substantially decreased the amount of streamflow available for irrigation. Increases in micro-irrigation acres, which can have efficiencies that exceed 90 percent and require 20–50 percent less water than sprinkler systems, likely contributed to reduced withdrawals in the lower CRB. For thermoelectric power, total withdrawals, including the use of reclaimed wastewater, were greater in the upper CRB from 1985 through 2005. In 2010, the lower CRB exceeded the upper by only 11,000 acre-feet. On average, thermoelectric consumptive use accounted for about 80 percent of the total withdrawals; however, consumptive-use data in the upper CRB was incomplete. Surface water was the primary source in the upper CRB and groundwater was the primary source in the lower CRB. In the CRB overall, water withdrawals for thermoelectric generation has decreased since 2000, except for groundwater withdrawals in the lower CRB. Power generation at thermoelectric plants was greater in the upper CRB from 1985 to 2000, and after 2005 the difference in power generation was small; however, the upper CRB continued to have more power generation. In both the upper and lower CRB, power generation increased from 1985 to 2005.

Arizona, Colorado, Nevada, New Mexico, Utah, Wyomi↗

USGS2026

Sediment vulnerability ranking for river basins across the contiguous U.S. using integrated biophysical and social-ecological data

Nearly half of streams and rivers in the United States (U.S.) have fair to poor conditions for aquatic ecosystem health as declared by the U.S. Environmental Protection Agency, and sediment was identified as a primary factor impairing these waterbodies. We rank sediment vulnerability using physical, ecological, and socioeconomic datasets in 163 4-digit Hydrologic Unit Codes within 18 regions across the contiguous U.S. based on the National Hydrography Dataset. We refer to sediment vulnerability as the potential for excess sediment to adversely impact social-ecological aspects of streams and rivers. Metrics were organized into six variable groups: (1) geomorphic setting, (2) modeled sediment and phosphorus, (3) hydrologic conditions, (4) anthropogenic factors and land use, (5) socioeconomic considerations, and (6) measures of ecosystem sensitivity. Correlations and principal component analysis were used to reduce and select metrics that explained the highest variability across basins. Results from the regional analysis identify basins with higher sediment vulnerability in each region, whereas national results identify hotspots of highly ranked basins in the Midwest and the central U.S. with a concentration of moderately to highly ranked basins in the south-central and southwestern U.S. Indicators of socioeconomic and ecological vulnerability integrated with physical drivers of sediment production help identify important gaps in sediment monitoring and research.

contiguous United States↗

USGS1984

Regional geohydrology of the northern Louisiana salt-dome basin, part II, geohydrologic maps of the Tertiary aquifers and related confining layers

Regional geohydrologic maps show the altitude of the base and the thickness of the aquifers of Tertiary age and related confining layers in the northern Louisiana salt-dome basin. The limit of freshwater in aquifers is also shown. The basin has an area of about 3,000 square miles, and four geologic units of Tertiary age contain regional aquifers. From oldest (deepest) to youngest, the aquifers are in the Wilcox Group, Carrizo Sand, Sparta Sand, and Cockfield Formation. As the Wilcox is hydraulically interconnected with the overlying Carrizo, they are treated as one hydrologic unit, the Wilcox-Carrizo aquifer. The aquifers are separated by confining layers that retard water movement. In the northwestern part of the area, the Wilcox-Carrizo aquifer is separated from the underlying sand facies of the Nacatoch Sand (Cretaceous age) by a confining layer composed of the Midway Group (Tertiary age) and the underlying Arkadelphia Marl and an upper clay and marl facies of the Nacatoch Sand (both of Cretaceous age). In the remainder of the area, the Wilcox-Carrizo aquifer is separated from an underlying Cretaceous aquifer comprised of the Tokio Formation and Brownstown Marl by the Midway Group and several underlying Cretaceous units which in order of increasing age are the Arkadelphia Maril, Nacatoch Sand, Saratoga Chalk, Marlbrook Marl , and Annona Chalk. The Wilcox-Carrizo aquifer is separated from the Sparta aquifer by the overyling Cane River Formation. The Sparta aquifer is separated from the Cockfield aquifer by the overlying Cook Mountain Formation.

Louisiana↗

USGS2025

Water use across the conterminous United States, water years 2010–20

Withdrawals of water for human use are fundamental to the evaluation of the Nation’s water availability. This chapter provides an analysis of public supply, crop irrigation, and thermoelectric power water use for the conterminous United States (CONUS) during water years 2010–20. These three categories account for about 90 percent of water withdrawals in the Nation. The values presented here are based on modeling approaches that estimate water use at temporal (monthly) and spatial scales (12-digit hydrologic unit code—small watersheds sized 50–100 square kilometers) compatible for integration into a broader national assessment of water availability. Models also provide an understanding of factors that influence water use. An estimated 244,817 million gallons per day (Mgal/d; 28,677 million cubic meters per month [Mm 3 /mo]) were withdrawn on average within the CONUS during water years 2010–20 from fresh water and saline water for crop irrigation, public supply, and thermoelectric power, with shares of 43, 14.5, and 42.5 percent for each of these categories, respectively. In the same period, estimated withdrawals and consumptive use (1) for public supply were 35,400 and 4,219 Mgal/d (4,081 and 486 Mm 3 /mo), respectively; (2) for crop irrigation were 105,497 and 75,698 Mgal/d (12,147 and 8,716 Mm 3 /mo), respectively; and (3) for thermoelectric power from fresh water were 82,656 and 2,904 Mgal/d (9,952 and 345 Mm 3 /mo), respectively. Withdrawals for these categories of water use are highly spatially variable, with western States dominated by crop irrigation and eastern States dominated by thermoelectric-power water use. Public supply accounts for the largest percentage of water use in several heavily populated northeastern States. Reliance on groundwater compared to surface water depends on the availability of water sources and the type of water use. For public supply, withdrawals from groundwater are greater than withdrawals from surface water in the Western aggregated hydrologic regions, whereas the balance shifts to more surface water for the rest of the CONUS. In all aggregated hydrologic regions, the predominant source of water for crop irrigation is groundwater. Most thermoelectric power facilities in the eastern half of the CONUS use surface water from freshwater and saline sources; most thermoelectric power facilities in the western half of the CONUS use groundwater.

conterminous United States↗

USGS2007

The influence of river regulation and land use on floodplain forest regeneration in the semi-arid upper Colorado River Basin, USA

Flow regulation effects on floodplain forests in the semi-arid western United States are moderately well understood, whereas effects associated with changes in floodplain land use are poorly documented. We mapped land cover patterns from recent aerial photos and applied a classification scheme to mainstem alluvial floodplains in 10 subjectively selected 4th order hydrologic units (subbasins) in the Upper Colorado River Basin (UCRB) in order to document land use patterns (floodplain development) and assess their effects on Fremont cottonwood forest (CF) regeneration. Three of the mainstem rivers were unregulated, five were moderately regulated and two were highly regulated. We classified polygons as Undeveloped (with two categories, including CF) and Developed (with five categories). We ground-truthed 501 randomly selected polygons (4-28% of the floodplain area in each subbasin) to verify classification accuracy and to search for cottonwood regeneration, defined as stands established since regulation began or 1950, whichever is most recent. From 40% to 95% of the floodplain area remained undeveloped, but only 19-70% of the floodplain area was classified as forest. Regeneration occupied a mean of 5% (range 1-17%) of the floodplain. The likelihood of the presence of regeneration in a polygon was reduced 65% by development and independently in a complex manner by flow regulation. Our analyses indicate that floodplain forests may be in jeopardy on both regulated and unregulated rivers and that information on historical forest extent is needed to better understand their current status in the UCRB. Conservation efforts need to be coordinated at a regional level and address the potentially adverse affects of both flow regulation and floodplain development.

River Research and Applications↗

USGS2018

Estimates of nitrate loads and yields from groundwater to streams in the Chesapeake Bay watershed based on land use and geology

The water quality of the Chesapeake Bay may be adversely affected by dissolved nitrate carried in groundwater discharge to streams. To estimate the concentrations, loads, and yields of nitrate from groundwater to streams for the Chesapeake Bay watershed, a regression model was developed based on measured nitrate concentrations from 156 small streams with watersheds less than 500 square miles (mi2 ) at baseflow. The regression model has three predictive variables: geologic unit, percent developed land, and percent agricultural land. Comparisons of estimated and actual values within geologic units were closely matched. The coefficient of determination (R2 ) for the model was 0.6906. The model was used to calculate baseflow nitrate concentrations at over 83,000 National Hydrography Dataset Plus Version 2 catchments and aggregated to 1,966 total 12-digit hydrologic units in the Chesapeake Bay watershed. The modeled output geospatial data layers provided estimated annual loads and yields of nitrate from groundwater into streams. The spatial distribution of annual nitrate yields from groundwater estimated by this method was compared to the total watershed yields of all sources estimated from a Chesapeake Bay SPAtially Referenced Regressions On Watershed attributes (SPARROW) water-quality model. The comparison showed similar spatial patterns. The regression model for groundwater contribution had similar but lower yields, suggesting that groundwater is an important source of nitrogen for streams in the Chesapeake Bay watershed.

Chesapeake Bay watershed↗

USGS1999

A topological system for delineation and codification of the Earth's river basins

A comprehensive reference system for the Earth's river basins is proposed as a support to fiver basin management, global change research, and the pursuit of sustainable development. A natural system for delineation and codification of basins is presented which is based upon topographic control and the topology of the fiver network. These characteristics make the system well suited for implementation and use with digital elevation models (DEMs) and geographic information systems. A demonstration of these traits is made with the 30-arcsecond GTOPO30 DEM for North America. The system has additional appeal owing to its economy of digits and the topological information that they carry. This is illustrated through presentation of comparisons with USGS hydrologic unit codes and demonstration of the use of code numbers to reveal dependence or independence of water use activities within a basin.

Journal of Hydrology↗

USGS2018

Warming is driving decreases in snow fractions while runoff efficiency remains mostly unchanged in snow-covered areas of the western United States

Winter snowfall and accumulation is an important component of the surface water supply in the western United States. In these areas, increasing winter temperatures T associated with global warming can influence the amount of winter precipitation P that falls as snow S . In this study we examine long-term trends in the fraction of winter P that falls as S (Sfrac) for 175 hydrologic units (HUs) in snow-covered areas of the western United States for the period 1951–2014. Because S is a substantial contributor to runoff R across most of the western United States, we also examine long-term trends in water-year runoff efficiency [computed as water-year R /water-year P (Reff)] for the same 175 HUs. In that most S records are short in length, we use model-simulated S and R from a monthly water balance model. Results for Sfrac indicate long-term negative trends for most of the 175 HUs, with negative trends for 139 (~79%) of the HUs being statistically significant at a 95% confidence level ( p = 0.05). Additionally, results indicate that the long-term negative trends in Sfrac have been largely driven by increases in T . In contrast, time series of Reff for the 175 HUs indicate a mix of positive and negative long-term trends, with few trends being statistically significant (at p = 0.05). Although there has been a notable shift in the timing of R to earlier in the year for most HUs, there have not been substantial decreases in water-year R for the 175 HUs.

Arizona, California, Colorado, Idaho, Montana, Nev↗

USGS2013

A comprehensive evaluation of two MODIS evapotranspiration products over the conterminous United States: using point and gridded FLUXNET and water balance ET

Remote sensing datasets are increasingly being used to provide spatially explicit large scale evapotranspiration (ET) estimates. Extensive evaluation of such large scale estimates is necessary before they can be used in various applications. In this study, two monthly MODIS 1 km ET products, MODIS global ET (MOD16) and Operational Simplified Surface Energy Balance (SSEBop) ET, are validated over the conterminous United States at both point and basin scales. Point scale validation was performed using eddy covariance FLUXNET ET (FLET) data (2001–2007) aggregated by year, land cover, elevation and climate zone. Basin scale validation was performed using annual gridded FLUXNET ET (GFET) and annual basin water balance ET (WBET) data aggregated by various hydrologic unit code (HUC) levels. Point scale validation using monthly data aggregated by years revealed that the MOD16 ET and SSEBop ET products showed overall comparable annual accuracies. For most land cover types, both ET products showed comparable results. However, SSEBop showed higher performance for Grassland and Forest classes; MOD16 showed improved performance in the Woody Savanna class. Accuracy of both the ET products was also found to be comparable over different climate zones. However, SSEBop data showed higher skill score across the climate zones covering the western United States. Validation results at different HUC levels over 2000–2011 using GFET as a reference indicate higher accuracies for MOD16 ET data. MOD16, SSEBop and GFET data were validated against WBET (2000–2009), and results indicate that both MOD16 and SSEBop ET matched the accuracies of the global GFET dataset at different HUC levels. Our results indicate that both MODIS ET products effectively reproduced basin scale ET response (up to 25% uncertainty) compared to CONUS-wide point-based ET response (up to 50–60% uncertainty) illustrating the reliability of MODIS ET products for basin-scale ET estimation. Results from this research would guide the additional parameter refinement required for the MOD16 and SSEBop algorithms in order to further improve their accuracy and performance for agro-hydrologic applications.

Remote Sensing of Environment↗

USGS2018

Streamflow contributions from tribal lands to major river basins of the United States

While many studies on tribal water resources of individual tribal lands in the United States (US) have been conducted, the importance of tribal water resources at a national scale has largely gone unrecognized because their combined totals have not been quantified. Thus, we sought to provide a numerical estimate of major water budget components on tribal lands within the conterminous US and on USGS hydrologic unit codes (HUC2) regions. Using existing national-scale data and models, we estimated mean annual precipitation, evapotranspiration, excess precipitation, streamflow, and water use for the period 1971–2000. Tribal lands represent about 3.4 percent of the total land area of the conterminous US and on average account for 1.9 percent of precipitation, 2.4 percent of actual evapotranspiration, 0.95 percent of excess precipitation, 1.6 percent of water use, and 0.43 percent of streamflow origination. Additionally, approximately 9.5 and 11.3 percent of US streamflow flows through or adjacent as boundaries to tribal lands, respectively. Streamflow through or adjacent to tribal lands accounts for 42 and 48 percent of streamflow in the Missouri region, respectively; and for 86 and 88 percent in the Lower Colorado region, respectively. On average, 5,600 million cubic meters of streamflow per year was produced on tribal lands in the Pacific Northwest region, nearly five times greater than tribal lands in any other region. Tribal lands in the Great Lakes, Missouri, Arkansas-White-Red, and California regions all produced between 1,000 and 1,400 million cubic meters per year.

PLoS ONE↗

USGS2012

Predicting the likelihood of altered streamflows at ungauged rivers across the conterminous United States

An approach is presented in this study to aid water-resource managers in characterizing streamflow alteration at ungauged rivers. Such approaches can be used to take advantage of the substantial amounts of biological data collected at ungauged rivers to evaluate the potential ecological consequences of altered streamflows. National-scale random forest statistical models are developed to predict the likelihood that ungauged rivers have altered streamflows (relative to expected natural condition) for five hydrologic metrics (HMs) representing different aspects of the streamflow regime. The models use human disturbance variables, such as number of dams and road density, to predict the likelihood of streamflow alteration. For each HM, separate models are derived to predict the likelihood that the observed metric is greater than (‘inflated’) or less than (‘diminished’) natural conditions. The utility of these models is demonstrated by applying them to all river segments in the South Platte River in Colorado, USA, and for all 10-digit hydrologic units in the conterminous United States. In general, the models successfully predicted the likelihood of alteration to the five HMs at the national scale as well as in the South Platte River basin. However, the models predicting the likelihood of diminished HMs consistently outperformed models predicting inflated HMs, possibly because of fewer sites across the conterminous United States where HMs are inflated. The results of these analyses suggest that the primary predictors of altered streamflow regimes across the Nation are (i) the residence time of annual runoff held in storage in reservoirs, (ii) the degree of urbanization measured by road density and (iii) the extent of agricultural land cover in the river basin.

River Research and Applications↗

USGS2011

A geographic information system tool for aquatic resource conservation in the Red and Sabine River Watersheds of the southeast United States

Our goal was to build a geographic information system (GIS) tool to enhance modeling and hypothesis testing relevant to watersheds and fish fauna of the Red and Sabine Rivers in the southeastern United States. Species of concern were identified from wildlife action plans and Web sites. Spatial distributions of fish species and mercury in fillets were delineated using data from states. Public georeferenced data were obtained on land cover, soil type, forest canopy, impervious surfaces, wastewater facilities and 303(d) impaired waters. Overlay maps highlighted patterns across 8-digit hydrologic unit codes (HUCs). Bossier City, Louisiana and Beaumont, Texas areas displayed impervious surfaces over 10% and 303(d) waters per HUC were 20% and 8%, respectively. Because bowfin (Amia calva) (n=299) and bass (Micropterus spp.) (n=1493) occurred in up to 44% of HUCs and fillets contained elemental mercury concentrations across ranges monitored, they were appropriate indicators of bioavailable mercury. Of the total fish number showing >0.5ppm, 81% of records were derived from bowfin and bass, and stepwise multiple linear regressions indicated fish with mercury at these concentrations correlated with environmental variables. Detrended correspondence analysis showed total species occurrence and environmental relationships significant, where 81.6% of the variability in fish occurrence was explained by impervious surface, land cover other than canopy or impervious surface (such as wetlands and agricultural area) and canopy (forest type). Two-way indicator species analysis delineated species co-occurrence in HUCs (14 groups) and similarity of species composition (nine groups). Results identified three HUC groupings as potential targets for managerial interest. Quality control concerns for GIS development included site name data and priority rankings of critical fish species. This tool can be used to support modeling and trend analyses for several purposes, such as those relevant for developing and reporting on water quality standards and critical habitat assessments.

Arkansas, Louisiana, Oklahoma, Texas↗