How To Draw Flow Net Seepage By Hand
What is Velocity Potential and Stream Function?
Lakes are important habitats for a variety of species and have a high recreational value for people. Especially small lakes are considered to be ecologically very valuable.
These are crucial inputs for hydrological models and greatly affect soil water and salt movement. Knowledge of these properties is essential for the description and prediction of water and solute transport processes. The hydraulic properties such as infiltration, saturated and unsaturated conductivities and moisture-retention curves are strongly influenced by the soil physical properties such as texture, bulk density and organic matter.
These results stress that groundwater-surface water interactions in lakes should not be predicted from the studies on other lakes. The interactions are highly dependent on local hydrogeological conditions and theoretically derived seepage patterns are very likely not met in real-life situations. Soil-water-plant relationship is an essential component of hydrologic cycle.
The main driver has been groundwater abstraction, which has caused the formation of a cone of depression around the groundwater intake and forced lake water to seep towards the intake. A further increase in the abstraction rate in 2012 increased the outseepage area even further and brought about a lake-level drop. Though some of the recorded water-level drop can be attributed to lower groundwater recharge caused by meteorological conditions.
The method is often used in civil engineering, hydrogeology or soil mechanics as a first check for problems of flow under hydraulic structures like dams or sheet pile walls. As such, a grid obtained by drawing a series of equipotential lines is called a flownet.
Chapter 5: Flow Nets
The flownet is an important tool in analysing two-dimensional irrotational flow problems. Flow net technique is a graphical representation method.
Although they comprise a notable part of glacial terrain in northern Europe and America, the hydrology of lakes has been relatively understudied compared with the hydrology of streams and rivers. The protection of these ecosystems requires a thorough understanding of the functioning of the lakes’ hydrological regime. It has to be known how the ecosystem reacts to various factors that could affect its water-budget. The current thesis concentrated on decoding these issues in closed-basin lakes located in a highly valuable lake district in sandy glacial terrain in Estonia (Kurtna Lake District). In addition to natural factors that lake district is also affected by severe anthropogenic pressures.
A flow net generated to indicate flow of water to and from a hypothetical lake. Ground-water flow direction is indicated by flow lines (blue lines), and lines of equal hydraulic head (equipotential lines) are shown with dashed lines. Values shown are hydraulic head in the wells and surface-water stage. The subsurface catchment of Lake Stechlin is quite complex. Water level measurements in groundwater wells with different screen depths show that groundwater in the lake’s catchment may partly discharge to the lake and partly leak to deeper aquifers.
As these anthropogenic pressures mostly influence the status of subsurface water, then the major focus of the thesis was on the mechanisms of groundwater-lake water interactions. It was most likely the first study that scientifically addresses lake-groundwater interactions in Estonia. The wider aspiration of the thesis is to provide a cautionary example for managers and aspects to consider in research for scientists dealing with closedbasin lakes in similar hydrological and geological settings elsewhere around the world. The main results show that groundwater abstraction, variability of meteorological conditions and vegetation change on the catchment have all affected the water levels of the studied lakes in the last 60 year.
- Especially small lakes are considered to be ecologically very valuable.
- Although they comprise a notable part of glacial terrain in northern Europe and America, the hydrology of lakes has been relatively understudied compared with the hydrology of streams and rivers.
- Lakes are important habitats for a variety of species and have a high recreational value for people.
However, their theoretical description and measurements have been a difficult task for the scientists. Particularly, in Pakistan these properties have not been determined for the dominant soil series. Mostly this knowledge gap is filled by using pedo-transfer functions developed elsewhere in the world. For distributed modeling, fine scale estimation of soil physical and hydraulic properties is of prime importance. On the other hand, pedo-transfer functions are regions specific.
Rate of Seepage loss (Q)
Otherwise it is not possible to assure sustainable management of water resources and to preserve valuable ecosystems. The spatial pattern of groundwater seepage in the bottom of a more thoroughly studied lake revealed that seepage rate was not dependent neither on water depth, distance from the shore nor thickness of organic sediments.
2 Flow Nets by Analog Simulation
Soil is the medium that partitions precipitation into infiltration and runoff components. In all the processes of water movement in soil, its hydraulic properties play fundamental role, which in turn depend on soil physical properties and its water retention characteristics. Therefore, soil physical and hydraulic properties are very important to understand water flux in soil profile.
4 Saturated-Unsaturated Flow Nets
Pakistan has so far neither developed pedo-transfer functions nor hydraulic characteristics for its soils. Use of pedo-transfer functions developed elsewhere also lead to incredible results in the distributed hydrological modeling carried out for specific regions such as the Indus Basin.
The data generated by these procedures can meet the input requirements of the researchers working in the field of rainfall-runoff and river flow or flood forecasting. The method consists of filling the flow area with stream and equipotential lines, which are everywhere perpendicular to each other, making a curvilinear grid. Construction of a flownet is often used for solving groundwater flow problems where the geometry makes analytical solutions impractical.
Flow Net – Properties and Applications
Moreover, rainfall-runoff generate river flow regime, measurement of which is important for model calibration, flood forecasting, reservoir operation and diversions for various purposes. River discharge dynamics and fluvial processes further depend on physical nature of river channel, gradient, hydraulic structures and diversions. Knowledge of all these parameters and variables is fundamental to hydrological modeling and simulation studies. The objective of this manual is to provide step-wise procedure for determining soil physical and hydraulic properties as well as river channel characteristics and flow regime.
These results emphasise the importance of identifying groundwaterdependent surface water bodies and the mechanisms of the interactions before certified groundwater yields are set and water abstraction from the aquifer is started or the abstraction rates are increased. The results also stress that the full range of possible variability of the local meteorological conditions has to be taken into account.