Farm Dam SRG

For each dam, the Source conducts a water balance, considering inflows, rainfall, evaporation, seepage, water usage (demand), and overflow (spill) components (Figure 1-1) in each time step. This means that, for each time step (e.g., a day), each water balance component is accounted for in Source for every farm dam modelled.
The water surface area in the farm dam (A) will be used to calculate the volume from the depth (such as rainfall to the dam) and the area is estimated from the storage volume and/or parameters in three ways selected by the user:

1. Using the constant inputted maximum surface area at the farm dam as equation 1

   Equation 1

   At=C

   Where:
   C – Input parameters of Max. Dam Surface Area
   A_t - The surface water area at time step t
2. Estimated the area using the equation 2 with default parameters:

   Equation 2

   At=Vt-10.000636752211.071

   
   Where:
   V_t-1 - The surface water area at the previous time step t-1. If t=1 (the first running time step), it is the initial water volume at the farm dam
   0.0006367522 and 1.071 – the default values for parameters AFactor and BFactor, respectively
3. Estimated the area using the equation 3 with input parameters by the user

   Equation 3

   At=Vt-1a1b

   Where:
   a and b– the inputted values for parameters AFactor and BFactor, respectively
   The interstation inflow to a farm dam is the flow generated between the upstream node(s) and this dam, and it is estimated by Equation 4

   Equation 4

   ActIntStatFlowt=IntStatFlowFact * IntStatFlowReft*UnitC

   Where:
   ActIntStatFlowt – the Actual Interstation Flow volume, which is Interstation Flow Reference series scaled-down/up by the Scaling Factor, at the time step t
   IntStatFlowFact – the Scaling Factor, an input constant parameter
   IntStatFlowReft– the Interstation Flow Reference series at the time step t
   UnitC – Unit converter factor
   The total collected flow at the farm dam consists of two parts: the flow from the upstream node and (ii) and interstation inflow generated between the upstream node and this dam, shown in Equation 5

   Equation 5

   ToTCFlowt=USFlowt+ ActIntStatFlowt

   Where:
   ToTCFlowt - The total collected flow for the farm dam at the time step t
   USFlowt - The flow from the upstream node(s) of this fam dam at time step t
   The actual collected flow is then factored by equation 6:

   Equation 6

   ActDivFlowt =ToTCFlowt * DivFraction

   Where:
   ActDivFlowt - The estimated actual flow into the farm dam at the time step t
   DivFraction - The flow from the upstream node(s) of this fam dam at time step t
   However, the actual flow into the farm dam is related to the bypass flow. If the bypass flow capacity, an inputted parameter, for the farm dam is larger than or equal to the estimated actual flow, actual by-pass flow and actual inflow are estimated by equation 7. Otherwise, by equation 8:

   Equation 7

   ActByPassFlowt=ActDivFlowt ActInFlowt = 0

   
   

   Equation 8

   ActByPassFlowt=ByPassFlowCap ActInFlowt = ActDivFlowt - ByPassFlowCap

   
   Where:
   ByPassFlowCap - The bypass flow capacity, an inputted parameter
   ActByPassFlowt - The actual bypass flow, controlled by the bypass flow capacity and estimated actual inflow, at time step t
   ActInFlowt - The actual inflow to the farm dam, controlled by the bypass flow capacity and estimated actual inflow, at time step t
   The Rainfall volume to the farm dam is estimated by equation 9:

   Equation 9

   ActRainVolt=Raint* At

   Where:
   ActRainVolt - - The actual rainfall volume to the farm dam at time step t
   Raint - The inputted rainfall timeseries parameter at time step t
   The intermediate storage volume to the farm dam is estimated by equation 10:

   Equation 9

   Vt=Vt-1+ActInFlowt +ActRainVolt

   Where:
   Vt - The intermediate storage volume at time step t
   The seepage volume from the farm dam at time step is estimated by equation 10:

   Equation 10

   ActSeepageVolt=SeepageTSt* At If ActSeepageVolt > Vt: ActSeepageVolt =Vt Vt=0 Otherwise: Vt=Vt- ActSeepageVolt

   Where:
   ActSeepageVolt - - The actual seepage volume from the farm dam at time step t
   SeepageTSt- The inputted rainfall timeseries parameter at time step t
   Vt - The intermediate storage volume at time step t from equation 9
   The evaporation volume from the farm dam at time step is estimated by equation 11:

   Equation 11

   ActEvapVolt=Evapt* At If ActEvapVolt>Vt: ActEvapVolt=Vt Vt=0 Otherwise: Vt=Vt- ActEvapVolt

   Where:
   ActEvapVolt - - The actual evaporation volume from the farm dam at time step t
   Evapt- The inputted evaporation timeseries parameter at time step t
   Vt - The intermediate storage volume at time step t from equation 10
   The average annual water demand from the farm dam is estimated by equation 12:

   Equation 12

   AvgYearDemand=365.25*(i=1nDemandTSi)/n

   Where:
   AvgYearDemand - - The average annual demand volume from the reference data
   DemandTSi - The inputted water demand timeseries parameter at time step I, total time step is N in demand time series.
   
   The water demand from the farm dam at time step is estimated by equation 13.

   Equation 13

   ActDemandVolt=DemandTSt * DemandFactor*DamCap/AvgYearDemand If AvgYearDemand = 0, ActDemandVolt=0 If ActDemandVolt>Vt: ActDemandVolt=Vt Vt=0 Otherwise: Vt=Vt- ActDemandVolt

   Where:
   ActDemandVolt - The actual water demand volume from the farm dam at time step t
   DemandFactor - The inputted timeseries parameter at time step t
   DamCap - The inputted parameter of the farm dam capacity
   
   
   
4. 
   

The seepage volume from the farm dam at time step tis estimated by equation 9:

Where:
ActRainVolt - - The actual rainfall volume to the farm dam at time step t
Raint - The inputted rainfall timeseries parameter at time step t
ActSeepageVolt - - The actual seepage volume from the farm dam at time step t
SeepageTSt- The inputted rainfall timeseries parameter at time step t
ActEvapVolt - - The actual seepage volume from the farm dam at time step t
Evapt- The inputted rainfall timeseries parameter at time step t