How is the water flow described by the Richards equation?
The water flow is described by Richard’s equation: where θ is the volumetric water content (L 3 L − 3 ), t is time [T], z is the vertical coordinate [L], k is the unsaturated hydraulic conductivity [L T − 1 ], h is the pressure head [L], and S is a water mass source (positive) or sink (negative) (L 3 L − 3 T − 1 ).
How is the Richards equation related to channel geometry?
The dimensionless exponent a is related to the channel geometry. Flow in a cylinder, as in Hagen-Poiseuille’s law, results in a = 2, whereas flow along a plane or in a planar fissure, also referred to as the cubic law, results in a = 3. A. Samouëlian.
What are alternative approaches to the Richards equation?
Alternative approaches to the Richards equation dealing with transient water flow in unsaturated structured soils have to go back to the basic Navier–Stokes equations to avoid the assumption of equilibrium along the Ψ-θ relationship.
How does the Richards equation apply to soil?
However, Richards equation applies to flow in soils as long as momentum completely dissipates within a representative elementary volume, i.e., when the Richards condition is fulfilled. Preferential flow may expressly consider linear momentum and kinetic energy of transient flow in structured soils.
Where can I find graphs of water levels?
Zoom to a region of interest and hover over any dot to generate a hydrograph of recently observed water levels at that site. Some sites also offer water level forecasts for the next several days. How were these data collected? The majority of water level observations come from the U.S. Geological Survey’s national network of streamgages.
How to check river levels in the United States?
A color-coded map indicates current river levels or flood stages for more than 6,500 streamgages in U.S. states and territories. Zoom to a region of interest and hover over any dot to generate a hydrograph of recently observed water levels at that site. Some sites also offer water level forecasts for the next several days.
Where can I find real time water levels?
The majority of water level observations come from the U.S. Geological Survey’s national network of streamgages. Some real-time water level information comes from other federal, state, and local streamgage networks. NOAA River Forecast Centers issue forecasts for some streams and rivers.
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What We Do. The Office of Water (OW) ensures drinking water is safe, and restores and maintains oceans, watersheds, and their aquatic ecosystems to protect human health, support economic and recreational activities, and provide healthy habitat for fish, plants and wildlife.