Coupling to Reclamation's Surface Water Model to a Groundwater Model
This conducting proposal builds off a 2015 scoping study (in draft), which addresses the following question:
How can we improve Reclamation's capability to numerically model the interaction between surface water and
groundwater for various Mission related needs and goals?
Reclamation currently has a suite of surface water numerical models: a one-dimensional hydraulics and sediment
transport model, SRH-1D, and a two-dimensional hydraulics and sediment transport model, SRH-2D. Both have
extensive capabilities to predict surface water properties and interactions in rivers, reservoirs, canals, and other
hydraulic features. However, these surface water models do not address important interactions between the
surface water and groundwater.
Need and Benefit
Reclamation is responsible for the combined effort of meeting water delivery and aquatic habitat requirements.
Improving the modeling of the interaction between groundwater and surface water resources will help meet these
1. An understanding of the importance of hyporheic flow in stream channels. Hyporheic flow is the exchange
between groundwater and surface water in stream channels. Hyporheic zones are significant in the dynamics of
nutrients within the stream-catchment system (Bencala, 2005). For example, the exchange of nutrients due to
hyporheic flow in alluvial gravels is important for the survival of salmon eggs (Malcom et al, 2003). Consideration
of salmon egg survival is directly applicable to the improvement of the egg-to-smolt survival as part of
Reclamation designing and improving habitat conditions for ESA listed Salmonid and Steelheed species as part of
the FCRPS Biological Opinion.
2. Quantifying the amount of surface water seepage from rivers, reservoirs, or canals into groundwater features
(e.g. shallow or deep aquifers) is necessary to identify methods to improve water delivery and/or endangered
species habitat requirements.
3. The ability to describe and quantify the interaction of surface water and groundwater within alluvial fans
reduces the uncertainty in designing infrastructure and/or modifications within these highly dynamic systems.
Current methods to couple groundwater and surface water models ignore many two-dimensional surface flow
effects and are not able to represent complex stream geometries adequately (see
http://water.usgs.gov/ogw/modflow/). Further research on coupling the groundwater and surface water to
resolve smaller scale features of the interactions is necessary.
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