start:hype_model_description:hype_routing
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start:hype_model_description:hype_routing [2020/06/18 10:28] cpers [Simple outlet lake or dam (olake)] |
start:hype_model_description:hype_routing [2020/10/23 15:06] cpers [Basic assumptions] |
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| ===== Basic assumptions ===== | ===== Basic assumptions ===== | ||
| + | The HYPE model simulates most lakes and rivers in a conceptual way. The HYPE model can contain two types of rivers, local river and main river, and two types of lakes, local lakes and outlet lakes (Figure 1). The local river represent all ditches, streams, rivers within a subbasin that recieve only runoff within the subbasin. It is modelled as one conceptual river with a length, regardless of the actual distance runoff from different land has to travel through the subbasin. Similarly a local lake represents all lakes within a subbasin receiving inflow only from within the subbasin. The modelled local lake recieves a fraction of the flow in the local river. The fraction is defined as a fraction of the subbasin area. The main river is the river part(s) of a subbasin that water from upstream subbasins flows through. Depending on subbasin delieation it may be clearly defined or represent several tributaries that comes to the subbasin outlet. Finally the modelled outlet lake represents a lake located at the outlet of a subbasin. | ||
| - | The HYPE model can contain two types of rivers, local stream and main river, and two types of lakes, local lakes and outlet lakes (Figure 1). Local and main rivers are present in all subbasins and the length of each is calculated as the square root of the subbasin area. The length of the watercourses can be given as input. The river can be a SLC class and is then given an area, but rivers can also be one-dimensional (i.e. no fraction of the subbasin area are occupied by the river and no precipitation added to the river). All local runoff is entering the local river. Local lakes (ilake) receive a portion of the local runoff. The flow leaving the local river (including flow from local lake) goes to the main river of the same subbasin. If there are upstream subbasins their flow is added to the local flow when both flows flow into the main river. Outlet lakes (olake) receive the outflow from the main river, i.e. all upstream and local flows. | + | Local and main rivers are present in all subbasins and the length of each watercourse is calculated as the square root of the subbasin area, unless it is given as input. The river can be a SLC class and has then an surface area, but rivers can also be one-dimensional (i.e. no fraction of the subbasin area are occupied by the river and no precipitation added to the river). All runoff enters the local river. Local lakes (ilake) receive a portion of the local flow. The flow leaving the local river and the outflow from local lake, goes to the main river of the same subbasin. If there are upstream subbasins their flow is added to the main river together with the local flow. Outlet lakes (olake) receive the outflow from the main river, i.e. all upstream and local flows. |
| |{{:start:hype_model_description:lakeriveroverview.png?400|}}| | |{{:start:hype_model_description:lakeriveroverview.png?400|}}| | ||
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| === Hydraulic geometry and river rating curve === | === Hydraulic geometry and river rating curve === | ||
| - | River diagnostic variables can be calculated for the main river. A river water depth (//d//) and river velocity (//u//) can be calculated from hydraulic geometry for the main river. The equation coefficients are general (//c,f,k,m//). | + | River diagnostic variables can be calculated for the main river. A river water depth (//d//) and river velocity (//u//) can be calculated from hydraulic geometry for the main river and the calculated main river flow (//q//). In the case of updating of flow in a subbasin with no outlet lake, the updated (main river) flow is used. The equation coefficients are general parameters (//c,f,k,m//). |
| <m> d=c*q^f </m> | <m> d=c*q^f </m> | ||
| <m> u=k*q^m </m> | <m> u=k*q^m </m> | ||
| - | + | ||
| - | where //c,f,k// and //m// are given by general parameters. | + | |
| With a given rating curve for main river flow, the water level of the river (//wr//) can be calculated by the inverse of the rating curve. Basin dependent values for reference level (//w0//) and the rating curve coefficients are input. Two rating curves may be given for each main river, one for general and ice free condition and one for use with ice on the river. The rating curve for ice conditions are only used if one is given for no ice conditions. | With a given rating curve for main river flow, the water level of the river (//wr//) can be calculated by the inverse of the rating curve. Basin dependent values for reference level (//w0//) and the rating curve coefficients are input. Two rating curves may be given for each main river, one for general and ice free condition and one for use with ice on the river. The rating curve for ice conditions are only used if one is given for no ice conditions. | ||
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| ==== Outlet lake as a multi-basin lake composed of lake basins ==== | ==== Outlet lake as a multi-basin lake composed of lake basins ==== | ||
| - | An olake can be part of a larger lake. It is then called a lake basin of the larger multi-basin lake. A multi-basin lake is assumed to have equal water level in all lake basins. The lake basins can have different depths below the outflow threshold, and they all use the same threshold when the water level output is calculated (same reference). | + | An olake can be part of a larger lake. It is then called a lake basin of the larger lake, which is called a multi-basin lake. A multi-basin lake is assumed to have equal water level in all lake basins. The lake basins can have different depths below the outflow threshold, and they all use the same threshold when the water level output is calculated (same reference). |
| === Inflow === | === Inflow === | ||
| - | A lake basin can get local inflow, inflow from upstream areas (that are not in the same multi-basin lake) and from the regional groundwater. Inflow works in the same way as for a simple olake (see above). | + | A lake basin can recieve local inflow, inflow from upstream areas (that are not part of the same multi-basin lake) and inflow from regional groundwater. Inflow works in the same way as for a simple olake (see above). |
| === Flow between lake basins === | === Flow between lake basins === | ||
| - | Flow through a lake divided into lake basins can occurs in both direction according to the maindown (and possibly branchdown). The implementation prioritize flow from nearby lake basins and flow in the downstream direction when calculation the flow betweeen lake basins to reach the equal water level. No internal threshold between lake basins is considered when the flows are calculated. | + | All lake basins of a multi-basin lake are connected by the main downstream path. They can in addition have branches within the multi-basin lake, where a fraction of the flow then goes. Flow through a lake divided into lake basins can occurs in both direction according to the maindown (and possibly branchdown). The implementation prioritize flow from nearby lake basins and flow in the downstream direction when calculating the flow betweeen lake basins. The flow between the lake basins are calculate to reach an equal water level. No internal threshold between lake basins is considered when the flows are calculated. |
| - | The flow out of a lakebasin is determined in several steps: | + | The flow out of a lakebasin (to another lakebasin) is determined in several steps: |
| - | - First the net outflow of each lakebasin is calculated. It is calculated as the difference between the current water level of the lakebasin and the water level of the whole lake after outflow from the lake. Thus the average water level of the lake is calculated and from this the outflow(s) of the lake. Considering these outflows leaving the lake, a new average water level is calculated that the lake will have after all flows between lakebasins have been moved. | + | - First the net outflow of each lakebasin is calculated. It is calculated as the difference between the current water level of the lakebasin and the water level of the whole lake after outflow from the multi-basin lake. First the average water level of the multi-basin lake is calculated, and from this the outflow(s) of the lake. Considering these outflows leaving the lake, a new average water level is calculated that the lake will have after all flows between lakebasins have been moved. This is the water level compared to the water level of the lakebasin in this step. |
| - | - The flow out of a lakebasin is the netflow plus all inflows from other lakebasins. The inflows are outflows of other lakebasins. Starting upstream in the lake the inflows are added to the outflow to give the flow out of every lakebasin. Note that these can be negative. | + | - The flow out of a lakebasin is the netflow plus all inflows from other lakebasins. Theses inflows are outflows of other lakebasins. Starting upstream in the lake the inflows are added to the outflow to give the flow out of every lakebasin. Note that these flows can be negative. |
| - The last step is to actually move the water. Preferably we want water to move from one lakebasin to the next, without mixing with water incoming from lakebasins further upstream. This we want so that substances do not travel all the way to the lake outlet on one time step. Therefore we try to remove all outflows from the lakebasins before we add the removed water into the downstream lakebasins. This might not be possible so we keep track of how much we can't move and repeat the third step if necessary. | - The last step is to actually move the water. Preferably we want water to move from one lakebasin to the next, without mixing with water incoming from lakebasins further upstream. This we want so that substances do not travel all the way to the lake outlet on one time step. Therefore we try to remove all outflows from the lakebasins before we add the removed water into the downstream lakebasins. This might not be possible so we keep track of how much we can't move and repeat the third step if necessary. | ||
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| - | The main outflow of the lake is assumed to be located in the last lake basin. Here outflow is estimated by a rating curve, either a specific equation or with the general equation, or by regulation routine. The threshold may be changing over the year as described in Section Two rating curves above. If the water level is below the threshold then the outflow is zero or if the production flow regulation is used there is production flow. See Section Production flow above. In addition the lake can have branched outflows out of the multi-basin lake from other lakebasins. The branched outflows is specified in LakeData and can be a rating curve or a production flow that uses the same thresholds as the main outlet. | + | The main outflow of the lake is assumed to be located in the last lake basin. Here outflow is estimated by a rating curve, either a specific equation or with the general equation, or by regulation routine. The threshold may be changing over the year as described in Section Two rating curves above. If the water level is below the threshold then the outflow is zero or if the production flow regulation is used there is production flow. See Section Production flow above. In addition the lake can have outflows out of the multi-basin lake from other lakebasins. These additional outflows are then the flow in the branch of these lakebasins. The outflow in a branch going out of the multi-basin lake is specified in LakeData for that lakebasin. It can be a rating curve or a production flow. If it is a production flow it uses the same thresholds as those for the main outflow of the multi-basin lake, i.e. //w0// and //wmin//. |
| ==== Initalisation of lake volume ==== | ==== Initalisation of lake volume ==== | ||
start/hype_model_description/hype_routing.txt · Last modified: 2024/01/25 11:37 (external edit)
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