![\"Figure](\"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/uploads\/sites\/4\/2020\/10\/figure-62-1024x673.jpg\")
Figure 62 -<\/strong> Groundwater flow (black arrows) in multiple, stacked, aquifer systems of the Coastal Plain of Virginia, USA. Aquifers are composed of terrestrial and marine sediments and separated by finer-grained marine sediments (confining units). Groundwater originates as recharge at both regional and local recharge areas associated with the shallow aquifer and at the western outcrop areas of the deeper confined aquifers. Groundwater flow is generally downward in the western portion of the region, horizontal in confined aquifers and then upward at the eastern regional discharge area located at the ocean (orange shading) (modified from Nelms et al., 2003).[\/caption]\r\n\r\nThis section addresses how to assess hydraulic gradients and flow directions using field data. It includes discussions of plotting and interpreting hydraulic heads; accounting for the influence of contrasts in and anisotropy of hydraulic conductivity on flow direction; as well as the effect of physical and hydraulic boundaries on groundwater flow directions and rates.","rendered":"The water in groundwater systems is always in motion. Groundwater flows from recharge areas (areas of high hydraulic heads) to discharge areas (areas of low hydraulic heads). Water enters the groundwater system in recharge areas and leaves the system in discharge areas. When striving to understand groundwater flow at one location, it is useful ask the question: Where is the water coming from and where is it going?<\/p>\n
Toth (1963) provided some foundation for conceptualizing groundwater flow systems. His work showed that multiple unconfined flow systems can occur in landscapes with sufficient recharge. He paired recharge and discharge areas to define the flow systems. He described three levels of flow systems: local, intermediate and regional, as shown in Figure 61. Local flow systems form between adjacent recharge and discharge areas, and local system flow paths are relatively short. Intermediate flow systems originate in recharge areas and discharge downgradient, but not to the nearest discharge location. Intermediate flow systems encompass at least one local flow system. Regional flow systems originate at regional recharge areas and flow to distant discharge locations, with relatively long flow paths. The regional system often surrounds one or more local and\/or intermediate flow systems.<\/p>\n Toth\u2019s conceptual model provides a framework for investigation of unconfined groundwater systems. Groundwater flow systems do not only occur in aquifers, groundwater moves through all the saturated materials between a recharge and discharge area. This can include multiple aquifers (unconfined, and confined) as well as aquitards as illustrated in Figure 62. Confined aquifers are recharged at outcrop sites or by downward leakage of water from overlying aquifers. In down gradient areas they may discharge in the form of upward leakage of water into overlying aquifers.<\/a><\/p>\n This section addresses how to assess hydraulic gradients and flow directions using field data. It includes discussions of plotting and interpreting hydraulic heads; accounting for the influence of contrasts in and anisotropy of hydraulic conductivity on flow direction; as well as the effect of physical and hydraulic boundaries on groundwater flow directions and rates.<\/p>\n","protected":false},"parent":0,"menu_order":8,"template":"","meta":{"pb_part_invisible":false,"pb_part_invisible_string":""},"contributor":[],"license":[],"class_list":["post-109","part","type-part","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-json\/pressbooks\/v2\/parts\/109","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-json\/pressbooks\/v2\/parts"}],"about":[{"href":"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-json\/wp\/v2\/types\/part"}],"version-history":[{"count":5,"href":"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-json\/pressbooks\/v2\/parts\/109\/revisions"}],"predecessor-version":[{"id":1156,"href":"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-json\/pressbooks\/v2\/parts\/109\/revisions\/1156"}],"wp:attachment":[{"href":"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-json\/wp\/v2\/media?parent=109"}],"wp:term":[{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-json\/wp\/v2\/contributor?post=109"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-json\/wp\/v2\/license?post=109"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"Schematic](\"https:\/\/books.gw-project.org\/hydrogeologic-properties-of-earth-materials-and-principles-of-groundwater-flow\/wp-content\/uploads\/sites\/4\/2020\/10\/figure-61-1024x491.jpg\")