Baseflow: Difference between revisions

Revision as of 14:55, 1 June 2019

Revision as of 14:46, 9 June 2019

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Baseflow is the portion of the [[streamflow]] that is sustained between precipitation events, fed to streams by delayed pathways. '''Baseflow''' (also called '''drought flow''', '''groundwater recession flow''', '''low flow''', '''low-water flow''', '''low-water discharge''' and '''sustained''' or '''fair-weather runoff''') is the portion of [[streamflow]] delayed shallow subsurface flow". It should not be confused with [[groundwater flow]]. Fair weather flow is called as Base flow.<ref>{{cite journal |author=Kendall and McDonnell

|year= 1998

|title= Isotope Tracers in Catchment Hydrology

|url= http://www.cof.orst.edu/cof/fe/watershd/research_publications_book.php

|publisher= Elsevier

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Baseflow is derived from [[bedrock]] [[water storage]] near surface [[valley]] [[soil]]s and [[riparian zone]]s. Water [[Percolation|percolates]] to [[groundwater]] and then flows to a [[body of water]]^. Baseflow depletion curve is the declining of baseflow/groundwater and soil reserves.<ref>{{Cite book|title=Environmental Hydrology, Second Edition|last=Ward, Andy and Trimble, Stanley|publisher=CRC Press|year=2003|isbn=978-1-4200-5661-7|___location=|pages=}}</ref> The volume and rate of water moving as baseflow can be affected by [[macropore]]s, [[micropores]], and other fractured conditions in the soil and shallow [[Geomorphology|geomorphic]] features. Infiltration to recharge subsurface storage increases baseflow. Evapotranspiration reduces baseflow because trees absorb water from the ground. In the fall baseflow can increase before it starts to rain because the trees drop their leaves and stop drinking as much water.<ref>{{Cite book|title=Key concepts in geomorphology|last=R.|first=Bierman, Paul|others=Montgomery, David R., 1961-, University of Vermont., University of Washington.|isbn=9781429238601|___location=New York, NY|oclc=868029499|date = 2013-12-27}}</ref> [[River incision]] can decrease the baseflow by lowering the [[water table]] and [[aquifer]].<ref name=":1">{{Cite book|title=California rivers and streams : the conflict between fluvial process and land use|author=Mount, Jeffrey F.|date=1995|publisher=University of California Press|isbn=9780520916937|___location=Berkeley|oclc=42330977}}</ref>

Good baseflow is connected to surface water that is located in permeable, soluble, or highly fractured bedrock. Bad baseflow is in [[crystal]]line or massive bedrock with minor fracturing and doesn't store water. Losing reaches is when the water flow decreases as it travels downstream and is fracturing deeper than surface water or in karst geology because limestone and dolomite high storage. Gaining reaches is when flow increases as it travels downstream. Gaining reaches are common in humid mountainous regions where the water table is above the surface water and the water flows from high head to low head following [[Darcy's law]].<ref name=":1" />

== Measuring Baseflow ==

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== Anthropogenic effects ==

[[Human impact on the environment|Anthropogenic]] effects to baseflow include [[forestry]], [[urbanization]], and [[agriculture]]. Forest cover has high infiltration and recharge because of tree roots. Removal of forest cover can have short term increase in mean flow and baseflow because less interception and [[evapotranspiration]].<ref name=":0" /> Urbanization includes a re-organization of surface and subsurface pathways so that water is flushed through catchments because of reduced hydraulic resistance, [[Manning's n|Manning's n]], channels and impervious surfaces which decreases infiltration. In urban areas water is often imported from outside the watershed from deep wells and [[reservoir]]s. The pipes that transport the water often leak 20-25% to the subsurface which can actually increase baseflow. Agriculture can lower baseflow if water diverted from stream for irrigation, or can raise baseflow if water is used from a different watershed. Pastures can increase compaction and reduce organic matter with reduces infiltration and baseflow.<ref name=":0" />

==See also==