SoilK
This module is defined in ClassSoilK and handles soil moisture accounting throughout the year. When snow cover is present, the input to this module is the infiltration (snowinfil) generated by the modules crack, frozen etc. From the end of snow melt till late fall the infiltration (infil) is generated by the modules Greencrack, PrairieInfiltration etc. The soil is handled as two layers. The upper layer is called the recharge layer and represents the top soil. Evaporation can occur from the recharge layer, soil_moist (all layers) or none. The surface infiltration satisfies the recharge layer before being used by the lower layer. The excess water from both soil layers contribute to the ground water flow , depressional storage and then to sub surface flow. The depressional storage is allowed to drain to ground water and sub surface flow.The parameters soil_rechr_max and soil_moist_max represents the maximum soil moisture capacity for the two layers i.e. field capacity. Wilt occurs when the state variables soil_rechr and soil_moist are equal to zero.
ClassSoilK is derived from ClassSoil with the addition of processes to handle wetlands. These processes are described in upcoming papers by Shook et Al..
There is a variation (#1) to handle HRU runoff through a culvert.
Evaporation and subsurface runoff are handled after infiltration. The maximum amount of evapotranspiration over soil is calculated by the module evap. Priestley-Taylor is always used over culvert ponds and wetlands.
Observations
- none
Variables
- Sd (mm) - depression storage. State variable.
- gw (mm) - ground water storage. State variable.
- soil_rechr (mm) - soil moisture content of recharge zone, i.e., the portion of the soil profile from which water is withdrawn by evaporation - expressed as an equivalent depth (m3/m2). State variable.
- soil_moist (mm) - soil moisture content of the rooting zone of the major vegetation type on the HRU - expressed as an equivalent depth (m3/m2). State variable.
- soil_ssr (mm/int) - subsurface runoff from soil_rechr and depressional storage.
- cum_soil_ssr (mm) - cumulative subsurface runoff from soil_rechr.
- soil_ssr_D (mm/d) - daily accumulation of soil_ssr.
- rechr_ssr (mm/int) - Portion of excess soil water from a HRU that enters subsurface reservoirs.
- cum_rechr_ssr (mm) - Accumulation of Portion of excess from a HRU to ssr.
- soil_gw (mm/int) - excess from soil_moist and depressional storage that enters groundwater reservoirs.
- cum_soil_gw (mm) - cumulative portion of excess soil water from a HRU that enters groundwater reservoirs
- Sd_water_frac () - fraction of the maximum possible Sd HRU fraction that is under water.
- contrib_frac () - Fraction of the entire HRU area contributing water.
- wetlands_evap (mm/int) - Depth of water evaporating from wetlands using Priestley-Taylor.
- total_evap (mm) - Control variable based on running sum of evap.
- soil_gw_D (mm/d) - portion of excess soil water from a HRU that enters groundwater reservoirs in a day.
- soil_runoff (mm/int) - remainder of excess soil water.
- cum_soil_runoff (mm) - cumulative surface runoff.
- soil_runoff_D (mm/d) - daily accumulation of soil_runoff.
- cum_runoff_to_Sd (mm/int) - cumulative portion of runoff to depression storage.
- infil_act (mm/int) - Actual amount of water infiltrating the soil on each HRU.
- infil_act_D (mm/d) - Daily actual amount of water infiltrating the soil on each HRU.
- cum_infil (mm) - cumulative potential amount of water infiltrating the soil on each HRU. Contents of the variable "infil" are calculated in the infiltration module used.
- cum_infil_act (mm) - cumulative actual amount of water infiltrating the soil on each HRU.
- gw_flow (mm/int) - Drainage from HRU ground water reservoir.
- gw_flow_D (mm/d) - Daily drainage from HRU ground water reservoir.
- cum_gw_flow (mm) - Accumulation of excess soil water from a HRU that enters groundwater reservoirs.
- redirected_residual (mm*km^2/int) - redirected residual after topping up Sd and soil_rechar in Netroute/Netroute_D/Netroute_M/Netroute_M_D. Average over the basin.
- cum_redirected_residual (mm*km^2/int) - cumulative redirected residual after topping up Sd and soil_rechar in Netroute/Netroute_D/Netroute_M/Netroute_M_D. Average over the basin.
Culvert variables only in variation #1.
- culvert_Q (m^3/s) - flow in culvert.
- culvert_water_H (m) - depth of pond at culvert inlet.
- culvert_water_A (m^2) - surface area of culvert pond
- culvert_water_V (m^3) - volume of water in culvert pond
- culvert_water_O (m^3) - volume of water overflowing road
- culvert_evap (mm/int) - Depth of water evaporating.
- cum_culvert (mm) - Cumulative culvert HRU flow.
- cum_culvert_over (mm) - Cumulative culvert HRU overflow.
Parameters
- basin_area (km^2) - basin area.
- hru area (km^2) - HRU area.
- Sdmax (mm) - Maximum depression storage.
- Sdinit (mm) - Initial depression storage.
- soil_rechr_max (mm) - maximum moisture content of the soil recharge zone - expressed as an equivalent depth (mm3/mm2). Must be less than or equal to soil_moist.
- soil_rechr_init (mm) - initial moisture content of the soil recharge zone - expressed as an equivalent depth (mm3/mm2). Must be less than or equal to soil_moist_init.
- soil_moist_max (mm) - maximum available water holding capacity of rooting zone - expressed as an equivalent depth (mm3/mm2).
- soil_moist_init (mm) - initial moisture content of rooting zone - expressed as an equivalent depth (mm3/mm2).
- gw_max (mm) - Maximum available water holding capacity of ground water reservoir.
- gw_init (mm) - Initial value of available water in ground water reservoir.
- rechr_ssr_K (mm/d) - recharge ssr drainage factor.
- lower_ssr_K (mm/d) - lower column (soil_moist - rechr_mois) ssr drainage factor.
- soil_gw_K (mm/d) - The maximum amount of the excess soil water for an HRU that is routed directly to the associated groundwater reservoir each day- expressed as an equivalent depth (mm3/mm2).
- Sd_ssr_K (mm/d) - depression storage ssr factor.
- Sd_gw_K(mm/d) - depression storage groundwater factor.
- gw_K (mm/d) - daily ground water drainage from gw reservoir.
- Sd_water_frac_max () - Maximum fraction of the entire HRU area that can be water.
- contrib_frac_init () - Fraction of the entire HRU area contributing water.
- evap_threshold (mm) - Threshold evaporation necessary for setting the contribution fraction to zero.
- soil_withdrawal () - HRU evaporation withdrawal for soil type: 1= sand, 2= loam, 3= clay. Water availability is used to limit evaporation as decribed below.
- cov_type () - Vegetation cover type designation for HRU: "0 = no evaporation, 1 = bare soil or shallow crops (evaporation from the recharge layer only), 2 = crops, grasses, shrubs and trees (evaporation from all soil moisture).
- transp_limited () - Inhibits transpiration from the soil moisture layer when set to 1.
- soil_ssr_runoff () - soil column excess to interflow(ssr)/runoff (and possibly SD) interflow-0/runoff-1
Culvert variables only in variation #1.
- channel_slope () - soil slope to culvert.
- side_slope () - side soil slope mormal to culvert slope
- culvert_diam (m) - culvert diameter.
- culvert_water_Dmax (m) - maximum depth of pond at culvert inlet
- number_culverts () - number of culverts and efficiency factor. Zero = no culvert
Variable Inputs
- hru_evap (evap) (mm/int) or (mm/d). Programmed for an interval or daily value.
- infil (*) (mm/int).
- snowinfil (*) (mm/int) or (mm/d). Programmed for an interval or daily value.
- runoff (*) (mm/int) or (mm/d). Programmed for an interval or daily value.
- meltrunoff (*) (mm/int) or (mm/d). Programmed for an interval or daily value.
- hru_actet (*) (mm/int). Programmed as a put value.
- hru_cum_actet (*) (mm).Programmed as a state put value.
Notes
Set Sdmax to zero and soil_moist to non- zero to model HRU with no Depression or Pond storage.
Set Sdmax to non-zero and soil_moist to non- zero to model HRU with Depression storage.
Set Sdmax to non-zero and soil_moist to zero to model HRU with Pond storage.
The significant difference between Pond and Depression storage is that soil_runoff to Pond storage is unlimited to its maximum capacity whereas depression storage is also limited to (Sdmax-Sd)*(1-exp(-soil_runoff/Sdmax)).
The layer soil_rechr is part of the soil_moist zone. It is not a separate identity.
Evaporation from bare soil and shallow crops only occurs from the recharge layer. All other cover types have evaporation/transpiration from recharge and soil moisture layers.
transp_limited is provided to limit grasses, shrubs and trees to only the recharge layer when the vegetation limits transpiration during drought conditions.
infil, snowinfil and condensation are added to the recharge layer and then to soil_moist. The excess is next used to satisfy groundwater. The surplus is designated as soil_runoff. The incoming runoff and meltrunoff are added to soil_runoff. If depression storage is specified any soil_runoff is used to fill the depression storage to its maximum.
Soil Withdrawal Types.
Water availability controls evaporation withdrawal in 'smbal' and 'Soil'. Modified from Zahner(1967) by G.H.Leavesley.
1 - Sand, at pcts < 0.25, limited to 0.25*pcts*avail_evap,
2 - loam, at pcts < 0.5, limited to 0.5*pcts*avail_evap,
3 - clay, at pcts < 0.67 && pcts > 0.33, limited to pcts*avail_evap and at pcts < 0.33 limited to 0.5*pcts*avail_evap,
4 organic, unlimted availability,
where pcts = (soil moist)/(soil moist max).