|Articles (A), software (B), and FAQ's (C), on (sub) surface land drainage for agriculture and irrigation||
1. Agricultural drainage
B) - Free software and models
helps in modelling effective rainfall, recharge, water storage, runoff, drainage and discharge relations in hydrological catchment areas (watersheds) using
the concept of a nonlinear reservoir.
does calculations on horizontal subsurface drainage systems in agriculture, hydraulic head, depth and level of water-table in agricultural land, and drain spacing using the energy balance of groundwater flow but also the Darcy and continuity equation (mass balance of water). It includes drain entrance resistance and soil anisotropy of hydraulic conductivity (soil permeability for water), i.e. the horizontal and vertical hydraulic conductivity are different. Applicable to pipe/tile drains (drain pipes) and open ditches.
Calculates the spacing of wells, the shape, depth, and level of the watertable in vertical drainage systems using pumped wells. Like EnDrain, it permits aquifers with various different properties and, in addition, fully/partially penetrating wells.
a mathematical, numerical simulation model describing the relations between agriculture, crop rotation, irrigation, rainfall, potential and actual evaporation (evapotranspiration), climate, hydrology, depth and level of water-table, capillary rise, deep percolation, soil salinity and subsurface drainage by drains or wells, and reuse (conjunctive use) of ground and drain water from wells. It includes farmers' responses to water logging and soil salinity.
A simplified version of SaltMod with the advantage that calculations can be made for shorter time steps (e.g. weekly or monthly). SaltCalc can be used when field observations of irrigation, water table and soil salinity have been made and one wishes to develop a model for that situation. Normally, calibration of unknown values must be done using a range of values of the corresponding variable, running the model repeatedly for a number of time steps, and selecting from the range the value giving model results closest to observed values as the optimal value.
This model is somewhat similar to SaltCalc. On the one hand the water management options are fewer (e.g. re-use of drainage or well water for irrigation do not feature here), but the model is more modern in the sense that the variable input for each time step is given in a table so that the calculations over all the time steps are done in one go. Moreover, by inserting the observed values of soil salinity in the data table, the model optimizes the leaching efficiency of the soil.
a combination of Saltmod with a model of ground water flow and hydraulics to account for large spatial variation through a network of polygons. It includes phreatic (unconfined) aquifers as well as soil layers with slow vertical hydraulic conductivity (soil permeability for water) resulting in semiconfined (leaky) aquifers.
C) - Frequently asked questions