Simulation of soil moisture and other components of the hydrological cycle using a water budget approach

Abstract

. 1996. Simulating soil moisture and other components of the hydrological cycle using a water budget approach. Can. J. Soil Sci. 75: tlt_t[2. Accurate simulation of soil moisture content at any time of th. y.r, ir*i.po.tunt to a!.icutture in dry regions due to the vital role soil moisture plays in crop production' In certain applicationi, such as drought moiitoring, other components of the hydrologic cycle such as runoff, snowmelt runoff, deep drainage and evaporative loss must also be accurately estimated. The goal bf *rls stuOy was to develop a model wltich accurately accounts for the major components of the hydrologiial cycle in ordeito simulate soil moisture content for drought monitoring and crop yield prediction. Thi versatile soil moistuie budget (vsMB) was evaluated and modified to improve the prediction of soil moisture content, runoff from rainfall and snowmelt, drainage of moisture out of the root zone and soil surface temperature' The modified components of the model were independently testJd and validated using field and published data. The soil moisture output from our modified model correlated well with observed changes in soil moiJture during the growing season under wheat. fallow and over the winter. The moisture content of the surface layei was simulated with greater accuracy than that of deeper layers' The soil moish,,e simulated by the modified model compares bltter with measured values than that simulated using the original version o-f the VSMB. The simulation of snow dynamics at Lethbridge, a chinook-dominated region, gave credibility to the snowmelt runoff predicted by the model. Model Testing and ValidationThe crop coefficients that produced the best agreement between-simulated and observed soil moisture during the testing stage ( [1967][1968][1969][1970][1971][1972][1973][1974][1975][1976][1977][1978] using the original and modified VSMB. Measured moisture content (m3m'3) uous wheat at Lethbridge (Fig. a) (Fig. a).

Modelling nitrogen leaching in Prince Edward Island under climate change scenarios

“…In this study we employed the Residual Soil Nitrogen indicator ), coupled with a modified version of the Versatile Soil Moisture Budget Model (VSMB; Akinremi et al 1996) to compute longterm N leaching under a historic baseline climate and under four climate change scenarios. Further details on the methods, assumptions and data are given below.…”

“…As in previous versions of the VSMB, the new algorithm uses field capacity to determine water flow between layers (the so-called capacity based approach), but it is also linked to an empirical subroutine that accounts for both upward-and downward redistribution of soil water by unsaturated flow. Furthermore, Akinremi et al (1996) improved the surface runoff subroutine for rainfall and snowmelt.…”

“…Each day of the year, the net loss or gain is added to the water already in the soil. For infiltration and soil water redistribution, Akinremi et al (1996) incorporated the simple cascading algorithm of the Ceres-Wheat model (Ritchie and Otter 1985). As in previous versions of the VSMB, the new algorithm uses field capacity to determine water flow between layers (the so-called capacity based approach), but it is also linked to an empirical subroutine that accounts for both upward-and downward redistribution of soil water by unsaturated flow.…”

Simulated Canola Yield Responses to Climate Change and Adaptation in Canada

“…However, soil properties may not have any effects in simulations without water and N stress, that is, the simulations for potential yield discussed later. To take into account the year-to-year variations of seeding date, seeding dates in the simulations were estimated using the criteria developed by Bootsma and De Jong (1988), based on daily air temperatures, precipitation, and estimated soil moisture on a loam soil with an available water-holding capacity (AWC) of 150 mm by the Versatile Soil Moisture Budget model (VSMB) (Baier et al, 1979;Akinremi et al, 1996). Planting was assumed to start when 10 d had occurred after 15 April meeting the following criteria: 0.75T max + 0.25T min > 7°C; daily precipitation <2 mm; snow on ground <10 mm; SW 1 < 0.90 AWC 1 and SW 2 < 0.95 AWC 2 .…”

Spring emergence of CanadianDelia radicumand synchronization with its natural enemy,Aleochara bilineata

“…Daily maximum and minimum air temperatures, rainfall, and total precipitation (Environment Canada 2002) were used to estimate daily mean soil temperature at 5 cm depth with the soil-temperature algorithm in the modified versatile soil moisture budget (Akinremi et al 1996). Because daily solar radiation for the two sites was required for the versatile soil moisture budget, we estimated this using the Hargreaves formula for calculating solar radiation (Hargreaves and Samani 1982): ), and T max and T min are the daily maximum and minimum air temperature, respectively.…”