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One would not want the water table to be too shallow to avoid crop yield depression nor too deep to avoid drought conditions. This is a subject of drainage research. The figure shows that a seasonal average depth of the water table shallower than 70 cm causes a yield depression [5] The figure was made with the SegReg program for segmented ...
[2] [3] In hydrology, a water balance equation can be used to describe the flow of water in and out of a system. A system can be one of several hydrological or water domains, such as a column of soil, a drainage basin, an irrigation area or a city. The water balance is also referred to as a water budget. Developing water budgets is a ...
Water retention curve is the relationship between the water content, θ, and the soil water potential, ψ. The soil moisture curve is characteristic for different types of soil, and is also called the soil moisture characteristic. It is used to predict the soil water storage, water supply to the plants (field capacity) and soil aggregate stability.
The Palmer Drought Index is based on a supply-and-demand model of soil moisture. Supply is comparatively straightforward to calculate, but demand is more complicated as it depends on many factors, not just temperature and the amount of moisture in the soil but also hard-to-calibrate factors including evapotranspiration and recharge rates ...
SWAT is a continuous time model that operates on a daily time step at basin scale. The objective of such a model is to predict the long-term impacts in large basins of management and also timing of agricultural practices within a year (i.e., crop rotations, planting and harvest dates, irrigation, fertilizer, and pesticide application rates and timing).
Normally A increases with Q and S because the higher the water level is the higher the discharge capacity becomes. The factor is therefore called Aq instead of A. The non-linear reservoir has no usable unit hydrograph. During periods without rainfall or recharge, i.e. when R = 0, the runoff equation reduces to Q2 = Q1 exp { − Aq (T2 − T1 ...
These data are useful for evaluating models of near-surface water table dynamics. It is noteworthy that the SMVE advection-like term solved using the finite moisture-content method completely avoids the need to estimate the specific yield. Calculating the specific yield as the water table nears the land surface is made cumbersome my non ...
In dry soil, particles at this point experience a total overhead stress equal to the depth underground (5 meters), multiplied by the specific weight of the soil. However, when the local water table height is within said five meters, the total stress felt five meters below the surface is decreased by the product of the height of the water table ...