RainOff

This helps in hydrologic modelling of effective
rainfall, recharge, and water storage. It
calculates runoff, surface
drainage and discharge relations in hydrological
catchment areas (watersheds) using the concept of
a nonlinear reservoir. It contains a calculator
for agricultural drainage systems with pipes and
ditches.

NashMod

The NashModel, like RainOff, calculates surface
runoff and stream flow from rainfall. However,
instead of a nonlinear reservoir it uses a
cascade of linear reservoirs, an idea elaborated
by Nash. In some cases it yields better results
than RainOff, but in other cases absolutely not.
The model was developed recently and put on this
website on 17 August 2017.

FloodRoute

This hydraulic model does calculations on
flood wave transport in a river or channel section.
The model is based on the concept of a nonlinear
reservoir having an outflow function with two
parameters. Given the inflow and outflow waves
the parameters will be given an optimal value
securing the best fit of the observed and similated
(calculated) outflow wave. Once the parameters are
well established, they can be used to predict the
outflow wave for any conceived inflow wave.

EnDrain

This hydrologic model does calculations on
steadystate discharge by horizontal subsurface
drainage systems, hydraulic head,
as well as depth and level of watertable in
agricultural land. It comes up with a drain
spacing using the energy balance
of groundwater flow, but also the Darcy and
continuity equation (mass balance/budget 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. All is applicable to pipe/tile drains
(drain pipes) and open ditches for the control
of the shallow water table.

DrainCalc

This hydrologic model does calculations on
nonsteady (transient, fluctuating) state discharge
by horizontal subsurface drainage systems in
agricultural land. The changes in hydraulic head
(level of the water table) are also simulated.
The model uses the concept of a noninear
reservoir, like in the RainOff program. This
reservoir is characterized by reaction factor of
discharge and hydraulic head (watertable height) on
the recharge varying in time.
The program calculates the reaction factor from
discharge and head data, or it calculates discharge
and head given the parameters of the response
function. In addition, it provides the facility to
find the response function from the parameters of
the drainage system.
All this is applicable to pipe/tile drains
(drain pipes) and open ditches for the control
of the shallow water table.

HydrCond

This is a calculator for the hydraulic
conductivity of soils based on measurements of
discharge and level of the ground water table
in agricultural subsurface drainage systems.

WellDrain

This hydrologic model 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.
