Simulating water balance and evapotranspiration in a subsurface drained clayey agricultural field in high-latitude conditions

Figures & data

Figure 1. Drainage networks and measurement devices in the Nummela Experimental Field (Turunen et al. 2013).

Table 1. Parameters for the water retention curves derived by fitting the van Genuchten (1980) model to the measured values. Sections A to D as in Figure 1.

Parameters	Section A, 0.0–0.25 m	Section B, 0.0–0.25 m	Section C, 0.0–0.25 m	Section D, 0.0–0.25 m
α [m^−1]	2.008	2.548	2.886	3.561
c [–]	1.150	1.145	1.149	1.147
θr [m^3 m^–3]	0.100	0.100	0.100	0.010
θs [m^3 m^–3]	0.529	0.543	0.529	0.560
Parameters	Section A, 0.25–0.45 m	Section B, 0.25–0.45 m	Section C, 0.25–0.45 m	Section D, 0.25–0.45 m
α [m^−1]	0.437	0.273	0.412	0.333
c [–]	1.106	1.150	1.161	1.145
θr [m^3 m^−3]	0.100	0.100	0.100	0.100
θs [m^3 m^−3]	0.554	0.551	0.539	0.555
Parameters	Section A, 0.45–2.4 m	Section B, 0.45–2.4 m	Section C, 0.45–2.4 m	Section D, 0.45–2.4 m
α [m^−1]	0.678	1.072	0.679	0.576
c [–]	1.104	1.095	1.127	1.115
θr [m^3 m^−3]	0.100	0.100	0.100	0.100
θs [m^3 m^−3]	0.602	0.591	0.534	0.579

α = parameter of the van Genuchten (1980) model.

c = parameter of the van Genuchten (1980) model.

θ_r = residual water content.

θ_s = saturated water content.

Figure 2. Simulated and measured snow water equivalent (SWE), and cumulative simulated and measured drain discharge and tillage layer runoff in field Sections (a) B and (b) D in the calibration period 1 January–31 December 2011.

Figure 3. Average simulated groundwater table levels in soil macropores and matrix, and measured minimum and maximum depths in field Sections (a) B and (b) D in calibration period 1 January–31 December 2011.

Figure 4. Simulated and measured snow water equivalent (SWE), cumulative simulated and measured drain discharge and tillage layer runoff in field Sections (a) B and (b) D in validation period 6 May 2008–31 December 2009.

Figure 5. Average simulated groundwater table levels in soil macropores and matrix, and measured minimum and maximum depths in field Sections (a) B and (b) D in validation period 6 May 2008–31 December 2009.

Figure 6. Cumulative PET computed with different methods in 1 January 2008–31 December 2009.

Figure 7. Cumulative simulated drain discharge and tillage layer runoff with different ET scenarios in Sections (a) B and (b) D in 1 January–31 December 2011 as well as (c) B and (d) D in 6 May 2008–31 December 2009.

Figure 8. Average simulated groundwater table levels in soil macropores and matrix with different ET scenarios in Sections (a) B and (b) D in 6 May 2008–31 December 2009.

Table 2. Components of the simulated water balance [mm] with different PET estimates in the whole field area during the validation period 6 May 2008–31 December 2009.

Scenario	PET07	PETCropc	PETClassA
Precipitation	1023	1023	1023
Potential ET	595	741	818
Actual ET	547	647	666
Evaporation from snow cover	13	13	13
Flow to open ditches	105	83	81
Drain discharge	157	117	108
Groundwater outflow	157	137	127
Change of storage	59	40	42
Mass balance error	−13	−15	−13

Turunen M, Warsta L, Paasonen-Kivekäs M, Nurminen J, Myllys M, Alakukku L, Äijö H, Puustinen M, Koivusalo H. 2013. Modeling water balance and effects of different subsurface drainage methods on water outflow components in a clayey agricultural field in boreal conditions. Agr Water Manage. 121:135–148. 10.1016/j.agwat.2013.01.012

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van Genuchten, M.Th. 1980. A closed-form equation for predicting the hydraulic conductivity of unsaturated soils. Soil Sci Soc Am J. 44:892–898. 10.2136/sssaj1980.03615995004400050002x

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