Title: 2.7. Hydrology — ctsm CTSM master documentation

URL Source: https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Hydrology/CLM50_Tech_Note_Hydrology.html

Markdown Content:
The model parameterizes interception, throughfall, canopy drip, snow accumulation and melt, water transfer between snow layers, infiltration, evaporation, surface runoff, sub-surface drainage, redistribution within the soil column, and groundwater discharge and recharge to simulate changes in canopy water \\(\\Delta W\_{can,\\,liq}\\), canopy snow water \\(\\Delta W\_{can,\\,sno}\\) surface water \\(\\Delta W\_{sfc}\\), snow water \\(\\Delta W\_{sno}\\), soil water \\(\\Delta w\_{liq,\\, i}\\), and soil ice \\(\\Delta w\_{ice,\\, i}\\), and water in the unconfined aquifer \\(\\Delta W\_{a}\\) (all in kg m\-2 or mm of H2O) ([Figure 2.7.1](#figure-hydrologic-processes)).

The total water balance of the system is

(2.7.1)[¶](#equation-7-1 "Permalink to this equation")\\\[\\begin{split}\\begin{array}{l} {\\Delta W\_{can,\\,liq} +\\Delta W\_{can,\\,sno} +\\Delta W\_{sfc} +\\Delta W\_{sno} +} \\\\ {\\sum \_{i=1}^{N\_{levsoi} }\\left(\\Delta w\_{liq,\\, i} +\\Delta w\_{ice,\\, i} \\right)+\\Delta W\_{a} =\\left(\\begin{array}{l} {q\_{rain} +q\_{sno} -E\_{v} -E\_{g} -q\_{over} } \\\\ {-q\_{h2osfc} -q\_{drai} -q\_{rgwl} -q\_{snwcp,\\, ice} } \\end{array}\\right) \\Delta t} \\end{array}\\end{split}\\\]

where \\(q\_{rain}\\) is the liquid part of precipitation, \\(q\_{sno}\\) is the solid part of precipitation, \\(E\_{v}\\) is ET from vegetation (Chapter [2.5](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Fluxes/CLM50_Tech_Note_Fluxes.html#rst-momentum-sensible-heat-and-latent-heat-fluxes)), \\(E\_{g}\\) is ground evaporation (Chapter [2.5](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/Fluxes/CLM50_Tech_Note_Fluxes.html#rst-momentum-sensible-heat-and-latent-heat-fluxes)), \\(q\_{over}\\) is surface runoff (section [2.7.2.1](#surface-runoff)), \\(q\_{h2osfc}\\) is runoff from surface water storage (section [2.7.2.1](#surface-runoff)), \\(q\_{drai}\\) is sub-surface drainage (section [2.7.5](#lateral-sub-surface-runoff)), \\(q\_{rgwl}\\) and \\(q\_{snwcp,ice}\\) are liquid and solid runoff from glaciers and lakes, and runoff from other surface types due to snow capping (section [2.7.6](#runoff-from-glaciers-and-snow-capped-surfaces)) (all in kg m\-2 s\-1), \\(N\_{levsoi}\\) is the number of soil layers (note that hydrology calculations are only done over soil layers 1 to \\(N\_{levsoi}\\); ground levels \\(N\_{levsoi} +1\\) to \\(N\_{levgrnd}\\) are currently hydrologically inactive; [(Lawrence et al. 2008)](https://escomp.github.io/ctsm-docs/versions/master/html/tech_note/References/CLM50_Tech_Note_References.html#lawrenceetal2008) and \\(\\Delta t\\) is the time step (s).

![Image 1: ../../_images/hydrologic.processes.png](https://escomp.github.io/ctsm-docs/versions/master/html/_images/hydrologic.processes.png)

Figure 2.7.1 Hydrologic processes represented in CLM.[¶](#id11 "Permalink to this image")

