Hydrology

- Control of excess water - (flood storm mitigation, storm drainage, bridges, sewerage)

- Conservation (quantity) - (water supply, irrigation, hydropower, navigation)

- Conservation (quality) - (pollution control)

Der Niederschlagsinput kommt zeitlich verzögert am Einzugsgebietsauslass (Pegel) an. Diese zeitliche Verzögerung (Retention) ist abhängig von den Speichereigenschaften und der Grösse des Einzugsgebietes.

The sun (solar energy) drives evaporation of water from oceans, lakes, moisture in the soil, and other sources of water.

Evaporation from soil and Transpiration from plants.

Precipitation that does not reach the soil, but is instead intercepted by the leaves, branches of the plants and the forest floor.

Infiltration is the process by which the water on the ground surface enters the soil.

Interflow is the lateral movement of water in the unsaturated zone, that first returns to the surface or enters a stream prior to becoming groundwater.

\(P(\Delta t)=Q(\Delta t)+E(\Delta t)+(S(t)-S(t-1))\)

\(P\) : precipitation

\(Q\) : runoff

\(E\) : evapotranspiration

\(S\) : reservoir

2.5 % of the global water reserves is sweet water.

- tilting siphon

- tipping bucket

- weighing

used for estimation of areal rainfall (basin precipitation)

1. Connect the raingauges (red)

2. Draw lines perpendicular to the connections (green)

For estimation of areal rainfall (basin precipitation)

Isoyets = Lines of equal precipitation

Method for estimation of areal rainfall (geostatistical methods)

Method for estimation of areal rainfall (geostatistical methods)

- Frontal Precipitation

- Convective Precipitation

- Orographic Lifting

How much rain falls (depth) in a certain time (duration) and their annuality (frequency).

Method widely used for frequency-analysis of heavy precipitation events.

The intensity over a given time (duration) and their annuality (frequency).

\(R_n\): Net-Radiation

\(R_si\): Incoming short-wave radiation

\(R_r\): Outgoing short-wave radiation

\(R_b\): Outgoing long-wave radiation

Land/ground cover controls the permeability at the ground surface and below.

- rock --> impermeable (unless fractured)

- bare soil --> permeability depends on soil material (sand/lime/clay), generally does NOT favour infiltration

- vegetated cover (grassland, forest,...) --> permeable, favours infiltration

SCS - Soil Conservation Service (from US-Department of Agriculture)

CN - Curve Number:

function of hydrologic soil type and land cover

Hortonian mechanism --> infiltration excess

Runoff generation occurs when the rainfall rate exceeds the infiltration capactiy (rate of infiltration)

Dunnian mechanism --> saturation excess

Whenn the unsaturated zone gets saturated the excess becomes runoff.

Fundamental equation to simulate the soil water content over time \(\frac{\partial \theta}{\partial t}\) in a given direction.

- Interflow

- Baseflow

- Direct runoff