start:hype_model_description:hype_land
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start:hype_model_description:hype_land [2018/10/16 08:35] cpers [Links to file reference] |
start:hype_model_description:hype_land [2020/02/07 12:48] cpers [Infiltration] |
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| Some additional output variables are calculated from the soil state variables. | Some additional output variables are calculated from the soil state variables. | ||
| - | === Ground water level === | + | === Groundwater level === |
| - | A water table is calculated for each soil layer (//gwat//) from the proportion of water-filled pores of effective porosity. If the ground water reaches above the surface, the water is calculated with 100% porosity. | + | The groundwater level is measured negative from surface (0m) to bottom of the soil layers. A positive groundwater level means that the soil surface is below water. If the ground water table reaches above the surface, the water is calculated with 100% porosity. |
| - | IF(soil(k)-wp(k)-fc(k)>0.0) | + | The water table is found in the lowest soil layer that is not completely filled with water. Soil layers above this layer may have water in its effective porosity, but that is not included in the groundwater level output variable. |
| - | gwat(k) = (soil(k)-wp(k)-fc(k)-ep(k))/ep(k) * soillayerthick(k) – | + | The water table for a soil layer is calculated linearly from the proportion of water-filled pores of effective porosity part of the soil pore volume. If the soil moisture of a soil layer is at field capacity (or below), the groundwater level of that soil layer is at the bottom of the layer. If the pore volume is filled, the groundwater level of that soil layer is at the top of the layer. |
| - | soillayerdepth(k-1) | + | |
| - | IF(gwat(1) > 0) gwat(1) = (soil(1)-wp(1)-fc(1)-ep(1))/1000. | + | |
| - | The water table measured as a negative from ground surface to bottom. A positive ground water table means that the land is under water. | ||
| - | The lowest soil layer that is not completely filled with water is defined as the "official" ground water table layer and is the one being printed. Soil layers above this may have water in its effective porosity. | ||
| === Soil moisture deficit === | === Soil moisture deficit === | ||
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| <m> infilt0 = rainfall + melt </m> | <m> infilt0 = rainfall + melt </m> | ||
| - | If the sum is greater than the infiltration capacity, a part of the water will not infiltrate into the soil. The calculation of actual infiltration will consider effects of surface runoff, macropore flow and frozen soil. If the calculated infiltration is greater than zero, it is added to the upper layer soil water. This is done regardless of whether there is space in the soil pores there or not. If the water exceeds the water pore volume it is assumed to lie on the ground, but it still belongs to the upper soil layer, is totally mixed and thus has the same concentrations. | + | Part of the available water for infiltration (//infilt0//) may not infiltrate into the soil, due to limitations by the soil's infiltration capacity and other properties of the soil. The calculation of actual infiltration will consider effects of surface runoff, macropore flow and frozen soil. If the calculated infiltration is greater than zero, it is added to the upper layer soil water. This is done regardless of whether there is space in the soil pores there or not. If the water exceeds the water pore volume it is assumed to lie on the ground, but it still belongs to the upper soil layer, is totally mixed and thus has the same concentrations. |
| HYPE has an option for alternative calculation order of soil processes during a timestep. As default it calculates and add infiltration (and let the soil water percolate) before runoff and evaporation is calculated and removed from the soil water. Alternatively runoff and evapotranspiration is calculated before infiltration and percolation to slow the response of soil runoff. These options is tested during development of the soil routine. | HYPE has an option for alternative calculation order of soil processes during a timestep. As default it calculates and add infiltration (and let the soil water percolate) before runoff and evaporation is calculated and removed from the soil water. Alternatively runoff and evapotranspiration is calculated before infiltration and percolation to slow the response of soil runoff. These options is tested during development of the soil routine. | ||
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| - | Surface runoff due to limitation in infiltration capacity and macropore flow are calculated from the sum of snow melt and rainfall, and are withdrawn from actual infiltration. | + | Surface runoff due to limitation in infiltration capacity and macropore flow are calculated from the sum of snow melt and rainfall; the available infiltration (//infilt0//). |
| - | If the sum is greater than the infiltration capacity (a threshold parameter, //mactrinf//), and the water in the upper soil layer is larger than another threshold (//mactrsm//) then macropore flow (//macroflow//) and surface runoff (//infoverflow//) may occur. These runoffs are caused by an inadequate infiltration capacity of the soil. Both these two flows are calculated as a percentage (//macrate// respective //srrate//) of the infiltration above the infiltration capacity threshold; | + | If the current infiltration rate is greater than a threshold (//mactrinf//, mm/timestep) then macropore flow (//macroflow//) and surface runoff (//infoverflow//) may occur. In addition the the water in the upper soil layer need to be larger than another threshold (//mactrsm//). The two flows are calculated as a percentage (//macrate// respective //srrate//) of the infiltration above the first threshold; |
| <m> macroflow = macrate * (infilt0 - mactrinf) </m> | <m> macroflow = macrate * (infilt0 - mactrinf) </m> | ||
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| An optional model for infiltration limitation and diversion of flow considers the effect of frozen soil. It is developed based on Zhao and Gray (1999). This model redirects all or part of the remaining infiltration, after calculating the diversion of surface runoff and macropore flow as described above. | An optional model for infiltration limitation and diversion of flow considers the effect of frozen soil. It is developed based on Zhao and Gray (1999). This model redirects all or part of the remaining infiltration, after calculating the diversion of surface runoff and macropore flow as described above. | ||
| - | If the minimum daily temperature is less than 10 degrees and the infiltration is larger than 5mm/d an icelens is created in the soil. In this case, and as long as the maximum daily temperature is below zero, the icelens redirect all infiltration to surface runoff and macropore flow. | + | If the minimum daily temperature is less than 10 degrees and the infiltration is larger than 5mm/d an ice lens is created in the soil. In this case, and as long as the maximum daily temperature is below zero, the ice lens redirect all infiltration to surface runoff and macropore flow. |
| <m> redirect = infilt </m> | <m> redirect = infilt </m> | ||
| - | If there is no icelens, but the soil temperature of the upper soil layer (//soiltemp//) is below zero the infiltration is restricted but not blocked. The infiltration is restriced by a potential infiltration adapted from Zhao and Gray (1999). The potential infiltration (//potinfilt//) depends on a model parameter (//bfroznsoil//) that is soil type dependent. It also depend on the "opportunity time" (//t0//), which is an estimate of the time with possible infiltration in hours; | + | If there is no ice lens, but the soil temperature of the upper soil layer (//soiltemp//) is below zero the infiltration is restricted but not blocked. The infiltration is restriced by a potential infiltration adapted from Zhao and Gray (1999). The potential infiltration (//potinfilt//) depends on a model parameter (//bfroznsoil//) that is soil type dependent. It also depend on the "opportunity time" (//t0//), which is an estimate of the time with possible infiltration in hours; |
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| ==== Soil temperature and snow depth ==== | ==== Soil temperature and snow depth ==== | ||
| - | Soil layer temperature (//soiltemp//) is calculated as a balance of three temperatures; previous time step soil layer temperature, soil temperature at deep depth (//deeptemp//) and air temperature (//temp//). The weight of the deep soil is constant (0.001), while the weight of the air temperature (//weightair//) depends on snow depth (//snowdepth//) and parameters. The soil memory (//soilmem//) depends on depth and land use, with parameters //surfmem// and //depthrel//. The memory of deep soil temperature is a general parameter (//deepmem//). | + | Soil layer temperature (//soiltemp//) is calculated as a balance of three temperatures; previous time step soil layer temperature, soil temperature at deep depth (//deeptemp//) and air temperature (//T//). The weight of the deep soil is constant (0.001), while the weight of the air temperature (//weightair//) depends on snow depth (//snowdepth//) and parameters. The soil memory (//soilmem//) depends on depth and land use, with parameters //surfmem// and //depthrel//. The memory of deep soil temperature is a general parameter (//deepmem//). |
| <m> soilmem = {lbrace}{ | <m> soilmem = {lbrace}{ | ||
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| <m> weigth_{air}={1}/{soilmem+10*snowdepth} </m> | <m> weigth_{air}={1}/{soilmem+10*snowdepth} </m> | ||
| - | <m> deeptemp=weight_{air}*temp+(1-weight_{air})*deeptemp </m> | + | <m> deeptemp=weight_{air}*T+(1-weight_{air})*deeptemp </m> |
| - | <m> soiltemp=weight_{air}*temp+(1-weight_{air}-weight_{deep} )*soiltemp+weight_{deep}*deeptemp </m> | + | <m> soiltemp=weight_{air}*T+(1-weight_{air}-weight_{deep} )*soiltemp+weight_{deep}*deeptemp </m> |
| In the default snow depth model, snow density (//snowdens//) depends on the snow's age in days (//snowage//). Snow density for fresh snow (//sdnsnew//) and the increase of density with snow age (//snowdensdt//) are general parameters (~ 0.1 and ~0.002). The snow's age increases by one every time step, but are weighted with age (0) for any new snow. | In the default snow depth model, snow density (//snowdens//) depends on the snow's age in days (//snowage//). Snow density for fresh snow (//sdnsnew//) and the increase of density with snow age (//snowdensdt//) are general parameters (~ 0.1 and ~0.002). The snow's age increases by one every time step, but are weighted with age (0) for any new snow. | ||
start/hype_model_description/hype_land.txt · Last modified: 2024/02/21 10:05 by cpers
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