[PDF]Rural Water Supply in Nepal-Hydrology Watercycle Course

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Rural Water Supply in Nepal: Hvdrologv-Water Cvcle
Course Technical Training Manual No. 1

Published by:

Remote Area and Local Development Department,

His Majesty's Government of Nepal/

Swiss Association for Technical Assistance/

United Nations Children's Fund

Kathmandu

Nepal

Available from:

United Nations Children's Fund

P.O. Box 1187

Kathmandu

Nepal

Reproduced by permission of UNICEF/Nepal .



Reproduction of this microfiche document in any
form is subject to the same restrictions as those
of the original document.




RURAL WATER SUPPLY NEPAL



TECHNICAL TRAINING
MANUAL no.l



HYDROLOGY-WATER CYCLE COURSE



Prepared And Published By
Remote Area And Local Development Department, HMG
SATA - Swiss Association For Technical Assistance
UNICEF - United Nations Children's Fund
Kathmandu 1977



HYDROLOGY - WATER CYCLE COURSE
Table of contents



1. Definition and hydrologic cycle 1

2. Climate , 3

3. Quantity and variation of rainfall

in Gandaki Zone (Nepal) 3

4. Rainfall, run off and infiltration 6

5. Drainage in Gandaki Zone.......... 7

6. Water Sources 10

6-1 Importance of water , 10

6-2 Ground-water 10

6-3 Springs 10

6-4 Wells 16

6-5 Rivers 18



* * * * * * *



HYDHOLOGY - WATER CYCLE COURSE



Definition and hvdrologic cycle

Hydrology is the science of distribution and behaviour of water
in nature »

Hydrology is a part of climatology* The cycle of water
(hydrologic cycle) is without beginning and end and consists
of the following:

Precipitation

All water from the atmosphere deposited on the surface of the
earth as either rain, snow, hail or mist.

Surface run off

The water which is derived directly from precipitation and passes
over ground into water courses. It is the precipitation less the
losses from infiltration and evaporation.

Evaporation, transpiration

Combined loss of, water from land and water-surface by evaporation
and vegetation transpiration.

Percolation

The term percolation describes the passage of water into,
through and out of the ground. Infiltration is the entrance
of the water into the ground and its vertical movement down
to the ground water table, while percolation (or ground
water flow) is applied to the movement of water after it has
reached the ground water table.



- 3 -



2, Climate



Concerning the year, the mai'i climatic features in Slepal ,
Grandaki Zone, are as follows:

- The raining season of the year, from -April to
September (monsoon)

- The dry season of the year, from October to
April*

3p Quantity and variation of rainfall
in Gandaki Zone, Nepal



Rainfall quantities can be mapped as for example

the following diagram for Pokhara town rainfall in 1975 •

The rainfall varies greatly throughout the year
and also from one year to the other as well as
from one station to another.



Stations


Rainfall amount in mm




Jan


Feb


Mar


Apr


May


Jun


Jul


Aug


Sep


Oct


Nov


Dec


Total
Annual


Max. in
24 hrs.


Khudibagar




55


24


140


235


677


923


555


620


154


00


3


3449


Ill

25 April


Bokhara


38


37


42


118


446


704


1177


650


1096


259


00


00


4767


171

1 July


Shyangja


29


37


32


123


401


654


1033


562


1

748


210


00


00


3829


195

3 August


Kunchha


32


71


23


41


272


603


740


452


604


85


00


00


2923


158

25 July


Bandipur


17


24


1


40


340


341


553


329


122


21


00


00


1788


102

27 July


Gorkha


24


30


15


63


176


188


343


250


285


22


00


00


1396


60
21 June


Chaparkot


38


20


33


107


210


674


472


472


609


11


00


00


2646


236

£0 June


Lumle


51


59


50


29


285


910


1719


1120


897


232


4


00


5356


188

1 July


Chase


28


46


13


1


2


90


262


128


126


42


18


00


756


61
1 July


Lamachaur


64


41


36


117


271


979


1261


783


1229


368


00


00


5149


175

5 Sept.












Rainfall


amount


in milinetera









POKHARA RAINFALL IN 1975



1200



1000



E

e



c
o

cr





!


I ! !






! !


!




D Months



Rainfall, run off and infiltration



The quantity of water running from an area into streams
and finally into the sea is not the same as the rainfall.

The quantity of rainfall will be shared into;

- direct evaporation

- transpiration through vegetation

- infiltration

- run off

Infiltrated water

It forms the ground water and through its natural filtration
it can be used directly as drinking water, only as far
as protective, measurements for catchment ire adopted.

The characteristics of the yield of a spring depend on the
type of soil and sub-soil. Prom rocky area the quantity
of water will directly depend upon the rainfall. Surface springs
will also dry up. shortly after the monsoon and supply again
after the first rains.

Springs from deep porous and water-holding covers, or

from far distant catchment areas, are more regular, but

their lowest supply quantity does not correspond with the lowest

rainfall

Run off

Similar characteristics can be found in streams. Rocky
areas provide flood and low water according to the rains.
Porous and water-holding soils supply the streams with
underground water and the quantity may "still decrease after the
first rains* Quantity of water may also varies because
of the snow when the melting time arises.



- 7 -

*5. Drainage in Gandaki Zone



HI VBi


Comes
from


r)T*a.i ns




Runs into
or forms


Gandaki
River


Tibet


East of

Gorkha

Diatt.


Gorkha &

Dhading

Distt.


Trisuli
river


Trisxili
River


Tibet


Central
region of
Gandaki
Zone


Dhading &

Nuvakot

Distt.


Budhi gandaki
River


Marsyangdi
River


Manang
Distt.


Manang &
Lam jung
Distt .


Gandaki
Zone
in the
middle


Budhigandaki
River


Modi
River


Annapurna
Mountains


Middle
part of
Gandaki
Zone




Budhigandaki
River


Seti
River


Machhapuchare
Mountains


Kaski
Distt.




Modi River


Kali gandaki
River


Tibet


Western
region


Gandaki
from

& Lumbini
Zone


Mix with
Budhigandaki

JL f nTmfl

IE X vllUO

Narayani
River


Modi
Stream


Machhapuchare
Mountains


Vest of
Gandaki
Zone


Kaski &
Parabat
Distt.


Kali gandaki
River


Andhi
Stream


South of
Pokhara


Syangja
Distt.




Kaligandaki
River



Important lakes in Gandaki Zone



In Pokhara is the Fewa lake which is partly used
for hydro-electric purpose with the help of a
dam at the lake outlet.



Near Bokhara there are also

two lakes ; Begnas lake
Rupa lake



In the north - west of Manang district is located
the Jilchl lake



- 9 -



DRAINAGE IN GANDAKI ZONE



legend:



▲
•



Zonal bundaries
District bundaries
Rivers , atrsasis
Motorable roads
Annapurna Mountains
District head




LAKES :

Few

(2) Rupa

Q) Begnash

® Tilchi



-10 -



6* Water sources

6,1 Importance of water

The water is very essential for :

- life

- health and sanitation

- as raw material for food production

- farming

- cattle '

The water conservation and the sanitation are important
to everyone.

6*2 Ground-water

The ground-water is the water which by percolating
through the ground reaches the ground water table.
The quality of the ground-water depends on:

a) The thickness of the stratum which covers the water-
bearing soil, this is important because of Indirect
contaminations like waste water, latrines and
fertilizers, etc*..

' b) The porosity of the sub-soil which influences the
natural filtration process*

The quantity of ground - water depends on x

a) The intake areas. It is important to realise that tb
topographical basin does not necessarily correspond
with the geological or hydrologioal drainage area*



- 11



b) Annual rainfall percolation. This depends on the
nature of the intake area, (kind of vegetation like
forest, farm, bush, grass field, ate..)

c) Perviousness of the ground* This depends on the
kind of material, stratification and its
homogenety.

d) Storage capacity. of the ground. This depends on the same
factors as perviousness and the intake area.

6.3 Springs



If ground-water leaves the ground without artificial
help, we call it spring-water.

Spring - water is usually the best water quality^

Whenever a water supply is planned, first investigation
should be made with possibility to nse a spring.

The quality and the quantity of the spring depends
on:

a) Intake area

b) Annual rainfall percolation



- 12



The continuous flow of a spring depends on the following
points :

a) Thickness of the stratum covers

b) Perviousness of the ground

c) Storage capability of the ground

Example of a spring influence by a single rainfall; This spring
will not have a constant flow;

- A thin stratum covers the water bearing soil

- The saturated stratum has a great perviousness (cracks and fissures)

- The water - bearing soil has little storage capability
(few pores which could be filled with water)

Example of a spring influenced only by annual rainfall * This spring
will have a good continuous flow volume :

- A thick stratum covers the water - bearing soil

- The saturated stratum has a small perviousness.

- The water - bearing soil has a big storage capability



- 13 -

Variation of ground water table and position of
springs according to season .




Saturated stratum
ll^H*si Clays

■ o — Wet season water table
_X— Dry season water table



Remarks :



SPRING


1 :


Wet


season =


large


fl ow






Dry


season =


snail


flow


SPRING


2 :


Wet


season =


normal


flow






Dry


season =


dry (


no water


SPRING


3 :


Wet


season =


normal


flow






Dry


season =


normal


flow



VARIOUS TYPE OF SPRINGS




Type 2




Saturated stratum



X



Ground water table



Type 3 .



15



SPRING




LEGEND :



Impermeable stratum



Saturated stratum



Pervious stratum



Ground water table



16 ~



6.4 Wells



A well is a round hole dug in the ground up to a certain
distance in the saturated stratum.

Wells make it possible to use the underground water
for economic applications as for water supplies or
irrigation purposes

The quality of the water obtained from a well
depends on :

a) The thickness of the stratum which covers the
water - bearing soil.

b) The porosity of the sub-soil.

The quantity of water obtainable from a well depends

on :

a) The intake area j

b) The annual rainfall percolation

c) The perviousness of the ground

d) The storage capability of the ground*

The different types of wells are as follows:

a) The shallow well which draws the water from the
permeable stratum between surface and the first
impermeable stratum*

b) The deep well which draws the water from a deep
saturated stratum unaffected by surface impurities*

c) The artesian well which has the similar characteristics
as the deep well except that it taps water under
pressure which will bring the water to the surface
under its own head*



- 17 -

TYPE OF WELLS .



a = shallow well
b = deep well




18



6,5 Rivers

The run-off water or stream -flow is the water which
is gathered into rivulets, brooks, streams or rivers •

The volume and variation of run-off are influenced
chiefly by the rainfall and its distribution by the
size, shape, cover and general topography of the
1 ■ catchment area, by the nature and condition of the
ground.

The melting of the snow also influneces the flow
of rivers.

For drinking purpose, the water of rivers should be
treated by sedimentation and filtration. Chemical
products, (chlorination) can be added for
elimination of bacteria. It will be the same
for lake water.



*#***##