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Hydrology viva questions

Hydrology questions and answere.

Hydrology viva questions and answeres.

1. What do you mean by hydrology ?

Hydrology is a science of water. Deals with the occurance, circulation and distribution of water of the earth and earth's atmosphere.

2. Name the components of hydrological cycle ?

The components of hydrological cycle are

Precipitation.
Infiltration.
Runoff.
Evaporation.
Evapotranspiration.
Transpiration.
Ground water.

Hydrological cycle.

3. What is precipitation ? List the different forms of precipitation ?

The term precipitation denotes all forms of water that reach the earth from the atmosphere. The different forms of precipitation are

Rain.
Snow.
Drizzle.
Glaze.
Sleet.
Hail.

4. What are the weather systems for precipitation ?

The different weather systems for precipitation are listed below

Front.
Cyclone.
Anticyclone.
Convective precipitation.
Orographic precipitation.

5. What are the different methods of recording of rainfall ?

Rain gauges are used to measure rainfall intensity and depth. Raingauges are classified into

Non recording Raingauges.

Symon's Raingauge.
Indian meterological department Raingauge.

Recording type Raingauges.

Tipping-Bucket type.
Weighing-Bucket type.
Syphon type.
Telemetering raingauges
Recording gauges

6. What is Runoff ?

Flowing of precipitation from catchment area through a surface channel.

7. What do you mean by hydrograph ?

Hydrograph is a graph consists of discharge in a stream versus time. Types of hydrographs depending on time are annual, monthly, seasonal and flood hydrographs.

8. What is unit hydrograph ?

Hydrograph of direct runoff due to one unit depth ( 1 cm ) of rainfall occuring uniformly over the basin at a uniform rate for a duration of specified D hours.

9. Define effective rainfall ?

Effective rainfall is that part of the rainfall that becomes direct runoff at the outlet of the water shed.
Effective rainfall is neither retained on the land surface nor infiltrated into soil.

10. Define Evaporation

Evaporation is a process by which liquid changes to gaseous state at the free surface, below the boiling point through heat of energy.

11. Define infiltration

Infiltration is the flow of water into the ground through the soil surface.

12. What is evapotranspiration ? Name the methods for measurements ?

Evapotranspiration is the sum of water loss to the atmosphere by plants through transpiration and water evaporated from soil or water body surrounding the plants.The measurement of evapotranspiration for given type of vegetation is carried out using two methods namely

Lysimeters.
Field plots.

13. Define aquifer, aquitard, aquiclude and aquifuge ?

Aquifer is a saturated formation of earth material which is not only stores water, but also yields sufficient quantity.
Seepage is only possible in aquitard. Thus yield is insignificant in comparision with aquifer.It is partly permeable.
Aquiclude is a geological formation. it is permeable and higly porous. Hence, it contains large amount of water.
Aquifuge is a geological formation is neither impermeable nor porous.

Design of rectangular sedimentation tank| waste water purification engineering

calculator for compressive strength of cube concrete

Design of Sedimentation tank

online design of rectangular sedimentation tank

Sedimentation tank purifies water by the process of sedimentation, which affects suspended particles to settle to bottom of tank. The density currents and turbulences caused by wind, typhoon or high tide carry these particles in water. In sedimentation tank, by controlling turbulence suspended particles in water settle to bottom of tank as sludge. The plain sedimentation in normal can remove as much as 70% of the suspended impurities present in water.

Factors effecting sedimentation are

Velocity of flow of waters : If the maximum permissible velocity of the flow reduces below 0.3m/sec gravity takes effect on suspended particles to settle.
Detention period : The detention time for plain sedimentation ranges from 4 to 8hours. For coagulant sedimentation ranges from 2 to 4hours.
Size and shape of particles : Particles in the size range of 0.5-5 μm are likely to deposit by sedimentation (Darquenne and Prisk 2004, O'Callaghan and Barry 1997, Pilcer and Amighi 2010, Stahlhofen et al. 1980).
Viscosity of water: High viscous fluid reduces the sedimentation. Sedimentation of oil and greasy substances reduces sedimentation efficiency.
Temperature: When temperature rises, sedimentation increases. The cold water reduces sedimentation process.

Maximum daily Demand of water purification Million liters/day.

Detention period in hours hours.

Velocity of flow centimeter/minute cm/minute.

To design sedimentation tank dimensions like length, width and height. We need three inputs namely maximum daily demand, detention period, velocity of flow, assume depth and free board. These mentioned variables are placed in input box. The page automatically calculates dimensions by clicking on calculate button.

Where,

Q_w = Maximum daily demand ( liters/day ).
Q_d_p = Quantity of water to be treated during the detention period.

\[\mathop Q\nolimits_{\mathop d\nolimits_p } = \frac{{\mathop Q\nolimits_w }}{{24}} \times \mathop d\nolimits_p \]

d_p = detention period ( hours ).

\[\mathop V\nolimits_{f - m} = \mathop V\nolimits_{f - cm} \times 10\]

V_f-m = Velocity of flow ( cm/minute or m/minute ).

\[\mathop L\nolimits_T = \mathop V\nolimits_{f - m} \times \mathop d\nolimits_p \]

L_T = Length of tank ( m ).

\[\mathop C\nolimits_s = \frac{{\mathop Q\nolimits_{\mathop d\nolimits_p } }}{{\mathop L\nolimits_T }}\]

C_s = Cross sectional are ( m² ).

\[\mathop W\nolimits_T = \frac{{\mathop C\nolimits_s }}{{\mathop D\nolimits_T }}\]

W_T = Width of tank ( m ).
D_T = Depth of tank ( m ).

Note: above mentioned formulas are used to design rectangular sedimention tank.

Quantity of water to be treated in 24hrs liters.

Quantity of water to be treated during detention period liters.

capacity of tank m³.

Length of tank m.

Area of tank m².

Assume Depth of tank m.{ Type the value here. }

Width of tank m.

Assume Free board m. { Type the value here. }

Overall depth of tank m.

Overall dimension of rectangular tank is

Length = m.
Width = m.
Height = m.

Web based calculator for forecasting population growth by arithmetic increase method | Environmental engineering

population forecasting by arithmetic increase method

Population forecasting by arithmetic increase method.

Arithmetic increase method

This method is based upon the assumption that the population increases at a constant rate. The rate of change of population with time is constant.

\[\frac{{dp}}{{dt}} = constant = K\]

\[dp = K \times dt\]

\[\int\limits_{\mathop p\nolimits_1 }^{\mathop p\nolimits_2 } {dp} = K \times \int\limits_{\mathop t\nolimits_1 }^{\mathop t\nolimits_2 } {dt} \]

\[\mathop p\nolimits_2 - \mathop p\nolimits_1 = K \times \left( {\mathop t\nolimits_2 - \mathop t\nolimits_1 } \right)\]

Where, suffixes 1 and 2 represent the last and first decades or census respectively. Thus t₂-t₁= Number of decades.

The population data for the last 4 to 5 decades, is therefore, obtained and the population increase per decade(x) is calculated; The average of which (x) is then used as the design growth rate for computing future population.

P₁= population after 1 decade from present

\[\mathop p\nolimits_1 = \mathop p\nolimits_0 + 1\overline x \]

P₂= population after 2 decade from present

\[\mathop p\nolimits_2 = \mathop p\nolimits_0 + 2\overline x \]

The general equation of arithmetic increase method is shown below

\[\mathop p\nolimits_n = \mathop p\nolimits_0 + n\overline x \]

Procedure

Collect 4 to 5 decades of population growth data. Input these data into table. The webpage performs analysis based on arithmetic increase method explained above. This webpage also plots graph.

Table

Years	Population	Increase in Population
1930	25000
1940	28000
1950	34000
1960	42000
1970	47000

Graph

This graph indicates population growth increase or decrease. Arithmetic increase method helps in rough estimate of population forecasting.

Population forecasting by arithmetic increase method.

Edit the population growth data of five decades by clicking on data.

Year	Population	Increase in Population
1930	25000
1940	28000
1950	34000
1960	42000
1970	47000

Click on the calculate to forecast population for three decades.

Average increase per decade =

Population after 1^st decade =

Population after 2^nd decade =

Population after 3^rd decade =

Forecasting population.

1. First video

2. Second video

Refrences

1. Lal , D & Upadhyay, A.K. (2013). Water Supply and Waste Water Engineering (2nd ed.). S.K. Kataria & Sons

2. Rangwala. (2016). Water supply and sanitary engineering (29nd ed.). Charotar Publishing House pvt. Ltd.

3. Chatterjee, A. K. (2006). Water Supply, Waste Disposal and Environmental Engineering (8th ed.). by Khanna Publishers.

4. Practical Handbook on Water Supply Engineering (2011).Nabhi Publications.

Online Simple graphical method for population growth | Water supply

Online Simple graphical method for population growth

Simple graphical method for population growth

Graph of population growth

This method helps plotting graph between population value and year. The curve can be used to estimate the population growth of desired year. This method gives approximate results, as the extension of the curve is done by the intelligence of the designer. This method can't accommodate sudden change in population growth, like sudden imposing of immigration restrictions, or compulsory family planning for eligible couples, or may develop enhanced medical facilitates thereby reducing death rates. Due to such reasons, the results obtained from these methods may or may not be precise.

Year	Population
1941	858545
1951	1015672
1961	1201553
1971	1691538
1981	2077820
1991	2585862
2001	3717820
2011	4517815
2021	5687890
2031	6589236

This method is less time consuming and used by engineers for check on results obtained by other methods like arithmetic increase, geometric increase and incremental increase methods. The above table shows population growth versus year data. From the data graph will be plotted, consisting of X and Y axes. X axis has been chosen as population and Y axis has years. This graph exhibits change in of population growth as shown in below figure.

Fig.1. Graph between population and year.