Hydrology

Rain near the village Lunde, The north of Funen, Denmark.

Content summary

Hydrology is the study of the water cycle. Natural and man-made processes guide water in its varied forms to a variety of ends. Use as irrigation, drinking water and process water by man is very common.

Learning Materials

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Hydrology Lessons

Diffusion

For a source contaminant concentration $\ C_0$ entering a flow of velocity $\vec U$ at a distance $\ x$ upstream from a point, the downstream concentration $\ C$ at that point is determined by the ratio...

$\frac{C}{C_0} = e^{\frac{x*\vec U}{D}}$

Where... $\ D$ is the local dispersion coefficient determined by $\ D = 0.067 * depth * V_f$

and where friction velocity is $V_f = \sqrt{g*depth*ChannelSlope}$

Velocity Distribution in an Open Channel (River)

Velocity distribution within a river follows a standard velocity profile for a confined space (pipe-flow)with the exception that the vertical distribution is truncated at the surface due to reduced friction with atmospheric gases versus the high friction against riverbed materials.

Boundary Layer thickness, also known as the displacement thickness, is defined by:

$\delta_d = \int_0^H \frac{1}{H} \left( 1-\frac{\vec u}{\vec U} \right) dz$

where $\vec U$ is the average velocity and $\vec u(x)$ is the velocity distribution in a channel of uniform depth $\ H$.

$\bar U = \frac{\int_A \left( \rho \vec V \cdot \hat n \right) dA}{\rho A}$

So in the case of this river, where the current is always normal to the cross-sectional area of the river (idealized)...

$\bar U = \frac{\int_x \int_y \left( \rho \vec V \right) dydx}{\rho A}$

Assignments

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Study guide:

• Physical Properties of the Oceans

1. Wikipedia article:Temperature
2. Wikipedia article:Density

References

Additional helpful readings include:

• MIT OCW - Transport Processes in the Environment course
• MIT OCW - Groundwater Hydrology course
• MIT OCW - Chemicals in the Environment: Fate and Transport course
• MIT OCW - Water Resource Systems course
• MIT OCW - Aquatic Chemistry course
• MIT OCW - Water and Sanitation Infrastructure in Developing Countries course
• MIT OCW - Environmental Microbiology course

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