What is the difference between percolation and runoff

Hydrological data are served as the foundations for investment activities in nearly all branches of the national economy; they are necessary especially for water management investments, such as the construction of dams, spillways and reservoirs, the alteration of water courses, and for flood-protection measures.

Detailed hydrological data are required for improving agricultural lands, mainly in the areas of irrigation, drainage, the construction of ponds, overall watershed improvements, anti-erosion protection, the controlling of streams and the like. There are plenty of studies regarding urban drainage, mentioned in the following text. Impermeable surfaces have impact on hydrology by eliminating through filtration dramatically increasing the volume of surface runoff.

Relationships between urbanization and subsurface drainage processes are described in several in-depth studies Price ; Hamel et al. They appear to be complex, based on the variation of natural drainage characteristics geology, topography, vegetation, etc. Hamel et al. Consequently, subsurface runoff in urbanized basins may increase or decrease.

Impervious surfaces result in a decrease in tapping, but reduction in vegetation in other permeable surfaces can reduce evaporation and potentially increase tapping.

So the loss of vegetation can reduce the intake, thus reducing the subsurface runoff Price ; Hamel et al. Urban drainage, sewerage and infrastructure can have important interactions with underground drainage processes. Berther et al. Interactions between water in the soil and sewer networks were modeled by Goebel et al.

Lowering the groundwater level Lee et al. In the research, they created a relationship between these classifications and the takeover behavior. The importance of incorporating geological data in hydraulic tomography surveys was proved by Zhao et al. The complexity of subsurface drainage processes means that predicting changes brought about by urbanization and urban infrastructure remains an important gap in our knowledge.

The development of appropriate tools and a common set of indicators is therefore a very important area of future research, especially in view of the growing importance of the role of subsurface effluent processes in water environment Hamel et al.

The purpose of this work is the proposal of conditions for percolation, which are derived from an analysis of precipitation, geological survey in the selected localities and from existing known equations for calculating the percolation of precipitation from surface runoff, for the needs of urban drainage.

The basis of a solution for urban hydrology consists in finding a favourable compromise alternative solution for the drainage of rainwater from the land. The subject of the survey described in this study is resolution of the infiltration of water from surface runoff and a comparison of the results obtained from field measurements, laboratory analysis, and numerical calculations. A field test uses the real measuring of precipitation with parallel percolation.

With laboratory analysis, a grading curve is determined and subsequently the filtration coefficient and numerical analysis deals with the modelling of percolation. Empirical relations and dimensional analysis belong under numerical analysis.

This section of the work deals with resolving the draining away of rainwater in specific locations on the basis of knowledge and measurement of qualitative and quantitative indicators of rainwater runoff. The city is situated at an elevation of m a. Lake and river sediments are also found here. The study was carried out in the buildings shown in Figure 2. Percolation shafts were located near the building of the computer center of PK6. Rainwater from the roofs of the buildings is carried into the percolation shafts A and B and subsequently percolated into the subbase.

In the grounds of TUKE, perhaps m from building PK6 is the LIC building, on the roof of which is equipment for measuring precipitation — a rain gauge serving for monitoring the amount of precipitation throughout the entire year. The shafts are located on the eastern side of the subject building PK6. The shafts are made from concrete rings with an external diameter of 1, mm. Both shafts are secured with a cast-iron hood. The shafts are similar in size; the difference of more than m 2 is in the surface of the roofing construction from which the rainwater is taken.

The made-ground is, for the most part, from gravelly clays, and the construction waste is made up of a pebble component of natural gravel. Geological boreholes have confirmed the thickness of the made-ground and the result was a value of 0. Under the made-ground an associated layer of flood-loam clays with a thickness of 4.

This is clay with moderate to low plasticity. Beneath the flood-loam sediments are gravels most often with a mixture of fine-grained soil with a thickness of 5. In the subbase of quaternary sediments there are neogenic clayey gravels and clays with a thickness of 0. The first measurements of precipitation began in March , at the building of the University Library in parallel with measurement of the amount of incoming rainwater and the height of the level of rainwater in percolation shaft A.

In March , similar measurements also began in percolation shaft B. The measuring instruments used and their placement in the percolation shafts are shown in Figure 3. Diagram of percolation wells and placement of instruments.

Instruments are identical in both shafts, but the YSI Yellow Springs Instrument Company multiparametric probe, levelogger and barologger are located only in shaft A. A table with the values of total precipitation [mm] and the values of rainfall intensities [mm. This table was used with a comparison of the graphically processed data on precipitation totals and the graphically processed maximum min and min precipitation intensities.

The percolation of precipitation waters into the rocky environment to a great measure depends on the local conditions, primarily from the measure of its permeability. The basic hydraulic characteristic of this measure is the filtration coefficient. Correctly determining its values represents a key question in the assessment of the percolation of water into rock or soil. As you can see in the picture above, ground water can intersect with surface streams, it can appear at the surface as springs, and it flows generally downhill toward the ocean.

How long does all this take? The time scales for the various processes above to occur vary widely. The evaporation process from the ocean and land surface is continuous, but the formation of clouds can take anywhere from seconds to hours.

It can occur for days. Generally, precipitation lasts from minutes to days, depending on whether there is a large source of atmospheric moisture feeding the system. Surface runoff of excess water can last from seconds to hours, usually. In large floods, the water may stay on land for days or weeks, as was the case during the Mississippi River flooding of and the Red River of the North flooding in Infiltration of rain into the topsoil usually starts immediately after the rain hits the ground and lasts until shortly after the rain stops.

Percolation through the soil may take minutes or days, depending on soil type, and how wet the ground was to begin with. Ground water Ground water moves veeeeerrrrrrry slowly, and a particle of water may take any where from days or months to years or even hundreds of years to move to the ocean, where it starts the process all over again.

This is a main reason why ground water supplies are impossible to artificially replenish after being depleted. You can't turn on a hose and fill the ground up, again. Wells go dry because the pump used to bring up ground water no longer reaches the water table.

The amount of rainfall that can infiltrate a given volume of soil is determined by the available empty space within the soil. For example, a given volume of soil with the soil moisture level at field capacity will infiltrate less rainfall than the same volume of soil at wilting point.

Thus, it is very important to know the soil moisture conditions when trying to model runoff from a storm. Soil texture determines the amount of water held for different moisture conditions. Clay-type soils have very small mineral particles and very small pores. Sandy soils have larger mineral particles and thus larger pore spaces.

Although it may seem counter-intuitive, smaller pore spaces in clay soil actually add up to a larger total amount of space than in an equivalent volume of sandy soil. Clay therefore has a higher percentage of soil water at field capacity compared to other soil texture types. Sandy soils, on the other hand, have larger mineral particles and larger pore space but have a smaller percent of porosity and corresponding lower percent soil moisture at field capacity and wilting point as compared to clay.

With sandy texture soils, the soil becomes saturated at a much lower percent of soil moisture. Click the image above to view animation. Water movement through soil is also influenced by its texture. Once the water has infiltrated the soil, it percolates downward. Sandy texture soils allow for more rapid water movement than clay texture soils. As a result, a clay texture soil will have higher soil moisture conditions for a longer period following precipitation than a sandy texture soil.

Simply stated, runoff is that portion of rainfall that does not infiltrate into the soil. In the case of a paved area, the expected runoff would equal the amount of rainfall minus evaporation and any small amount of surface storage.

As the soil becomes saturated, less infiltration will take place. For identical storms, the amount of storm runoff will vary depending on the soil moisture conditions. Sometimes less infiltration is available because of a previous storm. Infiltration rate is a measure of how fast water enters the soil. Inputs — precipitation including rain and snow, and solar energy for evaporation. Outputs — evaporation and transpiration from plants evapotranspiration , runoff into the sea, percolation of water into underlying rock strata.

Transfers or Flows — infiltration, Percolation, overland flow, throughflow, groundwater flow. Splash erosion or rain drop impact represents the first stage in the erosion process. Splash erosion results from the bombardment of the soil surface by rain drops. Results from the bombardment of the soil surface by raindrops.