Theory:

Glossary of difficult words from the lesson "Water - The Elixir of Life".
 
No.
Words
Meanings
1
elixira magical medicine; a hypothetical substance believed to cure all illnesses
2
draughta single act of drinking or inhaling
3
vainproducing no result; useless
4
billowingcharacterized by great swelling waves or surges
5
teemingbe full of or swarming with
6
siltgranular material of a size between sand and clay, whose mineral origin is quartz and feldspar
7
troughsa channel used to convey a liquid, like trenches
8
tricklingflow in drips, drizzle
9
quenchto satisfy thirst
10
precipitationwater that falls from the clouds towards the ground, especially as rain or snow
11
steamera ship, boat, or locomotive powered by steam
12
tractsan area of land, typically a large one
13
alluvial related to (alluvium) a deposit of clay, silt, and sand left by flowing floodwater in a river valley
14
importimportance
15
gulliesravines formed by the action of water
16
ravinesa deep, narrow pass with steep sides
17
rutsa long deep track made by the repeated passage of the wheels of vehicles
18
momentumthe force gained by a moving object
19
menacea thing that is likely to cause harm; a threat or danger
20
terracinga process of cutting pieces of sloped land into a series of successively receding flat surfaces or platforms, which resemble steps
21
bundsa long artificial mound of earth and stone, built to hold back water
22
artesian watera specific type of free-flowing, spring water that comes from underground wells
23
harnessingcontrol and make use of (natural resources), especially to produce energy
24
scrubvegetation consisting mainly of branches and twigs fallen from trees and shrubs
25
untoldtoo much to be measured 
26
subsidiaryless important than but related or supplementary to something
27
bargesconvey by a long flat-bottomed boat for carrying freight on canals and rivers
28
exhaustedcompletely used up, finished