Drainage equation

A drainage equation is an equation describing the relation between depth and spacing of parallel subsurface drains, depth of the watertable, depth and hydraulic conductivity of the soils. It is used in drainage design. A well known steady-state drainage equation is the Hooghoudt drain spacing equation. Its original publication is in Dutch. The equation was introduced in the USA by van Schilfgaarde. Hooghoudt's equation can be written as:. Q L2 = 8 Kb d (Dd - Dw) + 4 Ka (Dd - Dw)2 where: Q = steady state drainage discharge rate (m/day) Ka = hydraulic conductivity of the soil above drain level (m/day) Kb = hydraulic conductivity of the soil below drain level (m/day) Di = depth of the impermeable layer below drain level (m) Dd = depth of the drains (m) Dw = steady state depth of the watertable midway between the drains (m) L = spacing between the drains (m) d = equivalent depth, a function of L, (Di-Dd), and r r = drain radius (m) Steady (equilibrium) state condition In steady state, the level of the water table remains constant and the discharge rate (Q) equals the rate of groundwater recharge (R), i.e. the amount of water entering the groundwater through the watertable per unit of time. By considering a long-term (e.g. seasonal) average depth of the water table (Dw) in combination with the long-term average recharge rate (R), the net storage of water in that period of time is negligibly small and the steady state condition is satisfied: one obtains a dynamic equilibrium. Derivation of the equation For the derivation of the equation Hooghoudt used the law of Darcy, the summation of circular potential functions and, for the determination of the influence of the impermeable layer, de method of s and superposition. Hooghoudt published tables for the determination of the equivalent depth (d), because the function (F) in d = F (L,Di-Dd,r) consists of long series of terms.

About this result

This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.

Related concepts (13)

Related courses (5)

Related lectures (46)

ENV-549: Irrigation and drainage engineering

The course aims at teaching the fundamentals of both irrigation and drainage techniques with particular attention to the soil water balance and related management, the materials, the construction meth

ENV-222: Soil sciences

Le cours est une introduction aux Sciences du sol. Il a pour but de présenter les principales caractéristiques, propriétés et fonctions des sols. Il fait appel à des notions théoriques mais également

CIVIL-413: Urban hydraulic systems

Sustainable freshwater and urban drainage system are considered. For fresh water, the capture, reservoir and net are discussed. For the drainage, hydrology as well as the individual conduit and manh

Groundwater model

Groundwater models are computer models of groundwater flow systems, and are used by hydrologists and hydrogeologists. Groundwater models are used to simulate and predict aquifer conditions. An unambiguous definition of "groundwater model" is difficult to give, but there are many common characteristics. A groundwater model may be a scale model or an electric model of a groundwater situation or aquifer. Groundwater models are used to represent the natural groundwater flow in the environment.

Drainage system (agriculture)

An agricultural drainage system is a system by which water is drained on or in the soil to enhance agricultural production of crops. It may involve any combination of stormwater control, erosion control, and watertable control. While there are more than two types of drainage systems employed in agriculture, there are two main types: (1) surface drainage and (2) sub-surface drainage. Figure 1 classifies the various types of drainage systems. It shows the field (or internal) and the main (or external) systems.

Agricultural hydrology

Agricultural hydrology is the study of water balance components intervening in agricultural water management, especially in irrigation and drainage. The water balance components can be grouped into components corresponding to zones in a vertical cross-section in the soil forming reservoirs with inflow, outflow and storage of water: the surface reservoir (S) the root zone or unsaturated (vadose zone) (R) with mainly vertical flows the aquifer (Q) with mainly horizontal flows a transition zone (T) in which vertical and horizontal flows are converted The general water balance reads: inflow = outflow + change of storage and it is applicable to each of the reservoirs or a combination thereof.

Drainage in a cylinder ME-444: Hydrodynamics

Explores the drainage of a thin liquid film in a cylindrical cavity.

Retaining Walls: Design and Stability CIVIL-306: Geotechnical engineering

Explores the design and stability of various types of retaining walls in geotechnical engineering.

Slope Stability: Part 1 CIVIL-203: Soil mechanics and Groundwater seepage

Discusses slope stability, landslides causes, and reinforcement methods.