Water continuity in a river reach
For a one-dimensional incompressible reach, ∂(A+A_s)/∂t+∂Q/∂x=q_L balances conveying area A, additional nonconveying storage area A_s and discharge Q.
Key knowledge
For a one-dimensional incompressible reach, ∂(A+A_s)/∂t+∂Q/∂x=q_L balances conveying area A, additional nonconveying storage area A_s and discharge Q. Positive q_L adds water per unit channel length. Integrating between sections gives the rate of water-volume storage equal to upstream-minus-downstream discharge plus lateral input.
Values and equations
∂(A+A_s)/∂t+∂Q/∂x=q_L
- A,A_s
- conveying cross-sectional area and nonconveying storage volume per length m²
- Q
- volumetric water discharge m³ s⁻¹
- q_L
- net lateral water input per channel length m² s⁻¹
- x,t
- distance downstream and time m, s
Conditions and scope
- A_s is stored water volume per unit reach length, expressed as area; avoid counting the same floodplain volume in both A and A_s.
- A conservation equation needs a separate momentum/rating relation and boundary/initial data to predict a flood. Moving boundaries, density change and complex floodplain exchanges require consistent geometry.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Read the actual area, nonconveying storage and lateral-inflow equation1 and channel/floodplain split. Renamed source S to A_s to distinguish it from groundwater storativity; the integrated reach statement follows explicitly by integration. Excluded solver-version implementation claims and ambiguously worded exchange-sign prose.
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Entry details
Permanent link to this entry ↗- Record identity
- uni-earth-river-water-continuity
- Revision
- core.1
- Structured reference record
- University core expansion