Timothy A. Cohn (1957 – February 20, 2017) was an American hydrologist with the US Geological Survey, USGS Science Advisor for Hazards (1998–2001), and lecturer at Johns Hopkins University (2006 - ). Cohn served in the office of Senator Bill Bradley (D-NJ) in 1995-97 as a AAAS Congressional Science Fellow, and worked on the unsuccessful Bradley presidential campaign in 2000. After 2005, Cohn was a member of the Governing Board of the American Institute of Physics.
Cohn's research focused on flood frequency analysis, estimation of nutrient transport in rivers, and the interpretation of trends in hydroclimatological data. Cohn's most controversial research, which has not been fully embraced by the climate science community, suggests that the significance of climate trends may be greatly overstated because it does not consider the possibility that long-term persistence is a component of climatic variability.
Cohn held a B.A. in mathematics from Swarthmore College (1979) and M.A. (1984) and PhD (1986) degrees in water resource systems engineering from Cornell University.
Cohn was an avid marathoner and past president of the Reston Runners organization in Reston, Virginia.
Cohn was a board member of the Reston Association.
Hydrology is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and environmental watershed sustainability. A practitioner of hydrology is called a hydrologist. Hydrologists are scientists studying earth or environmental science, civil or environmental engineering, and physical geography. Using various analytical methods and scientific techniques, they collect and analyze data to help solve water related problems such as environmental preservation, natural disasters, and water management.
A stream gauge, streamgage or stream gauging station is a location used by hydrologists or environmental scientists to monitor and test terrestrial bodies of water. Hydrometric measurements of water level surface elevation ("stage") and/or volumetric discharge (flow) are generally taken and observations of biota and water quality may also be made. The locations of gauging stations are often found on topographical maps. Some gauging stations are highly automated and may include telemetry capability transmitted to a central data logging facility.
Water quality refers to the chemical, physical, and biological characteristics of water based on the standards of its usage. It is most frequently used by reference to a set of standards against which compliance, generally achieved through treatment of the water, can be assessed. The most common standards used to monitor and assess water quality convey the health of ecosystems, safety of human contact, extend of water pollution and condition of drinking water. Water quality has a significant impact on water supply and oftentimes determines supply options.
Surface runoff is the flow of water occurring on the ground surface when excess rainwater, stormwater, meltwater, or other sources, can no longer sufficiently rapidly infiltrate in the soil. This can occur when the soil is saturated by water to its full capacity, and the rain arrives more quickly than the soil can absorb it. Surface runoff often occurs because impervious areas do not allow water to soak into the ground. Furthermore, runoff can occur either through natural or man-made processes. Surface runoff is a major component of the water cycle. It is the primary agent of soil erosion by water. The land area producing runoff that drains to a common point is called a drainage basin.
Hockey stick graphs present the global or hemispherical mean temperature record of the past 500 to 2000 years as shown by quantitative climate reconstructions based on climate proxy records. These reconstructions have consistently shown a slow long term cooling trend changing into relatively rapid warming in the 20th century, with the instrumental temperature record by 2000 exceeding earlier temperatures.
Species distribution —or speciesdispersion — is the manner in which a biological taxon is spatially arranged. The geographic limits of a particular taxon's distribution is its range, often represented as shaded areas on a map. Patterns of distribution change depending on the scale at which they are viewed, from the arrangement of individuals within a small family unit, to patterns within a population, or the distribution of the entire species as a whole (range). Species distribution is not to be confused with dispersal, which is the movement of individuals away from their region of origin or from a population center of high density.
An hydrological transport model is a mathematical model used to simulate the flow of rivers, streams, groundwater movement or drainage front displacement, and calculate water quality parameters. These models generally came into use in the 1960s and 1970s when demand for numerical forecasting of water quality and drainage was driven by environmental legislation, and at a similar time widespread access to significant computer power became available. Much of the original model development took place in the United States and United Kingdom, but today these models are refined and used worldwide.
Groundwater recharge or deep drainage or deep percolation is a hydrologic process, where water moves downward from surface water to groundwater. Recharge is the primary method through which water enters an aquifer. This process usually occurs in the vadose zone below plant roots and, is often expressed as a flux to the water table surface. Groundwater recharge also encompasses water moving away from the water table farther into the saturated zone. Recharge occurs both naturally and through anthropogenic processes, where rainwater and or reclaimed water is routed to the subsurface.
R. Timothy Patterson is a professor of geology in the Department of Earth Sciences at Carleton University, Ottawa, Ontario, Canada. He is a Canadian researcher with specialization in paleolimnology, paleoceanography and paleoclimatology. He founded and is co-Director of the Carleton Climate and Environmental Research Group (CCERG) He has previously served as Director of the Ottawa-Carleton Geoscience Centre and as senior visiting fellow in the School of Geography, Queen's University of Belfast, Northern Ireland.
Robert M. Hirsch is a research hydrologist and a former Associate Director for Water of the U.S. Geological Survey. As Associate Director, he was responsible for the water science programs of the USGS. These include water-related research, the collection of data on rivers and ground water, assessments of water quantity and quality. He served as the leader of USGS water science from 1994 until May 12, 2008 when Dr. Hirsch transitioned to the USGS National Research Program to rededicate himself to advancing the science on critical issues of climate change and long-term trends in water resources.
A hydrologic model is a simplification of a real-world system that aids in understanding, predicting, and managing water resources. Both the flow and quality of water are commonly studied using hydrologic models.
Nutrient pollution, a form of water pollution, refers to contamination by excessive inputs of nutrients. It is a primary cause of eutrophication of surface waters, in which excess nutrients, usually nitrogen or phosphorus, stimulate algal growth. Sources of nutrient pollution include surface runoff from farm fields and pastures, discharges from septic tanks and feedlots, and emissions from combustion. Raw sewage is a large contributor to cultural eutrophication since sewage is high in nutrients. Releasing raw sewage into a large water body is referred to as sewage dumping, and still occurs all over the world. Excess reactive nitrogen compounds in the environment are associated with many large-scale environmental concerns. These include eutrophication of surface waters, harmful algal blooms, hypoxia, acid rain, nitrogen saturation in forests, and climate change.
The United States Geological Survey, abbreviated USGS and formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and the natural hazards that threaten it. The organization's work spans the disciplines of biology, geography, geology, and hydrology. The USGS is a fact-finding research organization with no regulatory responsibility. The agency was founded on March 3, 1879.
Harry F. Lins is a retired hydrologist whose career was spent with the U.S. Geological Survey from 1971 to 2012. During his years at USGS, his work spanned several Earth science disciplines, including coastal processes, surface water hydrology, and hydroclimatology. Although most of his career was spent conducting research, he managed the USGS Global Change Hydrology Program from 1989 to 1997, and served as Co-Chair of the Intergovernmental Panel on Climate Change (IPCC) Hydrology and Water Resources Working Group for the IPCC First Assessment Report. As a result of his IPCC work, he shared in award of the Nobel Peace Prize to the IPCC in 2007. In 1999, he and USGS colleague David Wolock developed "WaterWatch", the Nation’s first website depicting maps and graphs of water resources conditions in near real-time. Lins served as President of the World Meteorological Organization (WMO) Commission for Hydrology from 2012-2019.
Water quality modeling involves water quality based data using mathematical simulation techniques. Water quality modeling helps people understand the eminence of water quality issues and models provide evidence for policy makers to make decisions in order to properly mitigate water. Water quality modeling also helps determine correlations to constituent sources and water quality along with identifying information gaps. Due to the increase in freshwater usage among people, water quality modeling is especially relevant both in a local level and global level. In order to understand and predict the changes over time in water scarcity, climate change, and the economic factor of water resources, water quality models would need sufficient data by including water bodies from both local and global levels.
A water year is a term commonly used in hydrology to describe a time period of 12 months for which precipitation totals are measured. Its beginning differs from the calendar year because part of the precipitation that falls in late autumn and winter accumulates as snow and does not drain until the following spring or summer's snowmelt.
Nutrient cycling in the Columbia River Basin involves the transport of nutrients through the system, as well as transformations from among dissolved, solid, and gaseous phases, depending on the element. The elements that constitute important nutrient cycles include macronutrients such as nitrogen, silicate, phosphorus, and micronutrients, which are found in trace amounts, such as iron. Their cycling within a system is controlled by many biological, chemical, and physical processes.
Mary Catherine Hill is an American hydrologist, the winner of the Walter L. Huber Civil Engineering Research Prize and of the Dooge Medal of the International Association of Hydrological Sciences, a Darcy Lecturer for the National Ground Water Association, and Fellow of the American Geophysical Union. After working for many years at the United States Geological Survey, she became a professor of geology at the University of Kansas.
Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include non-salty mineral-rich waters such as chalybeate springs. Fresh water may encompass frozen and meltwater in ice sheets, ice caps, glaciers, snowfields and icebergs, natural precipitations such as rainfall, snowfall, hail/sleet and graupel, and surface runoffs that form inland bodies of water such as wetlands, ponds, lakes, rivers, streams, as well as groundwater contained in aquifers, subterranean rivers and lakes. Fresh water is the water resource that is of the most and immediate use to humans.
Paweł Mariusz Rowiński (born February 26, 1965 in Warsaw) – a Polish hydrogeologist, hydrodynamicist, geophysicist, full professor at the Institute of Geophysics, Polish Academy of Sciences, a full member of the Polish Academy of Sciences, Vice-President of the Polish Academy of Sciences.