Mass balance for Lysimeters 3, 4, 7 and 8

[danielgreen91]

Cumulative mass balance for Lysimeters 3, 4, 7 and 8

Cumulative mass balance plots expressed in litres between the user-selected date ranges showing inputs, storages and outputs for the following Lysimeters, similar to what is presented in the Figure below.

Lysimeter 3 (Cells A and B)
Lysimeter 4 (Cells A and B)
Lysimeter 7 (Cells A and B)
Lysimeter 8 (Cells A and B)

(Either a separate plot for each of the cells, or the option to turn Cell A and/or Cell B on or off on the same figure accordingly would be incredibly useful.

INPUTS:

Precipitation is the only input into the lysimeters at present. The input for the mass balance can be represented using 15 minute rainfall data ('Rain - 15 minutes') from the respective lysimeters (3, 4, 7, 8). To convert mm to volumetric (litres) units, multiple by two because the area of each cell is 2m^2:

cumsum(Rainfall)*2

STORAGES:

Volumetric water content (%) of the soil can be converted into litres of substrate water 'storage' based on the sensing area of each of the sensors at different depths. This can be done using the SoilVUE profile probe VWC data for Cells A and B (which gives 9 readings at 5cm, 10cm, 20cm, 30cm, 40cm, 50cm, 60cm, 75cm and 1m depths).

The volumetric 'change' can be based on the first reading (i.e. the user indicated start date). The following shows how this can be done for each of the sensors (note that each sensor has a different sensing volume because of the spacing of the sensor prongs:

VWC_50_3A = VWC_50_3A %>%
    mutate(VWC_50_diff = (A_SoilVUE_VWC_5cm....) - first(A_SoilVUE_VWC_5cm....)) %>%
           mutate(VWC_50_SuDS_diff_L = VWC_50_diff*0.1)'
 
VWC_100_3A = VWC_100_3A %>%
  mutate(VWC_100_diff = (A_SoilVUE_VWC_10cm....) - first(A_SoilVUE_VWC_10cm....)) %>%
  mutate(VWC_100_SuDS_diff_L = VWC_100_diff*0.1)

VWC_200_3A = VWC_200_3A %>%
  mutate(VWC_200_diff = (A_SoilVUE_VWC_20cm....) - first(A_SoilVUE_VWC_20cm....)) %>%
  mutate(VWC_200_SuDS_diff_L = VWC_200_diff*0.2)

VWC_300_3A = VWC_300_3A %>%
  mutate(VWC_300_diff = (A_SoilVUE_VWC_30cm....) - first(A_SoilVUE_VWC_30cm....)) %>%
  mutate(VWC_300_SuDS_diff_L = VWC_300_diff*0.2)

VWC_400_3A = VWC_400_3A %>%
  mutate(VWC_400_diff = (A_SoilVUE_VWC_40cm....) - first(A_SoilVUE_VWC_40cm....)) %>%
  mutate(VWC_400_SuDS_diff_L = VWC_400_diff*0.2)

VWC_500_3A = VWC_500_3A %>%
  mutate(VWC_500_diff = (A_SoilVUE_VWC_50cm....) - first(A_SoilVUE_VWC_50cm....)) %>%
  mutate(VWC_500_SuDS_diff_L = VWC_500_diff*0.2)

VWC_600_3A = VWC_600_3A %>%
  mutate(VWC_600_diff = (A_SoilVUE_VWC_60cm....) - first(A_SoilVUE_VWC_60cm....)) %>%
  mutate(VWC_600_SuDS_diff_L = VWC_600_diff*0.2)

VWC_750_3A = VWC_750_3A %>%
  mutate(VWC_750_diff = (A_SoilVUE_VWC_75cm....) - first(A_SoilVUE_VWC_75cm....)) %>%
  mutate(VWC_750_diff_L = VWC_750_diff*0.3)

VWC_1000_3A = VWC_1000_3A %>%
  mutate(VWC_1000_diff = (A_SoilVUE_VWC_100cm....) - first(A_SoilVUE_VWC_100cm....)) %>%
  mutate(VWC_1000_diff_L = VWC_1000_diff*0.5)

The total volume of soil storage (L) can then be calculated by summing all of the sensor volumes together into a cumulative plot from the user defined start date (note, some readings may be negative due to decreases in soil VWC following rainfall events).

OUTPUTS:

Outflow is the main loss from the lysimeters. Because the lysimeters are split into two 'cells', there are two outflows (A) and (B). Outflow should be expressed in litres, rather than ml:

cumsum(Outflow)/1000

Evapotranspiration accounts for a small loss, too. Evapotranspiration data from Lysimeter 6 can be used for all of the lysimeters (using 15 minute ETo Reference Grass variable on Lysimeter 6 for ET). Similarly to the rainfall, the account for the cell surface area, evapotranspiration (mm) data can be multiplied by two to convert the mm units into volumetric (L) units.

Plotting combined 'losses and storages' (i.e. Outflow + soil storage + ET), plus a mass balance (precipitation - combined losses and storages) would be useful for determining the overall mass balance of the system.