With 33.7% salinity, the Dead Sea is one of the world's saltiest bodies of water. The Dead Sea is landlocked and in the lowest valley on earth. All the minerals of the surrounding countryside get washed into one pool, which in turn gets baked by the sun. This concentrates the salts so much that the Dead Sea is 10 times as salty as the ocean.

The most abundant dissolved ions in seawater are sodium, chloride, magnesium, sulfate and calcium. Its osmolarity is about 1000 mOsm/l.

Wastewater effluent treatment is important way to control pollutants reaching in water bodies.

• Dissolved oxygen is the amount of free oxygen present in water which is not bound to any other element.
  
• If there is an increase in pollution rates dissolved oxygen rate drops drastically affecting aquatic life.
  

Acid rains: when the concentrations of oxides of nitrogen and sulphur increases in the air, rain water gets mixed up with these oxides to form acid rains.

Among the given options all are apt for the effects of acid rain except that it causes damage to the septic system.

It cannot cause damage to the septic system because most of the septic systems are underground and polluting such system with acids do not cause any adverse reaction to the environment.

Accelerated chemical weathering of building materials, damage to forests and crops, damage to aquatic organisms are the immediate effects of acid rains

A virus is a simple submicroscopic parasite of plants, animals, and bacteria in well water that can cause disease. It consists essentially of a core of RNA or DNA surrounded by a protein coat. Viruses are not living organisms and are unable to replicate without a host cell. Some viral infections often associated with drinking or bathing in contaminated water include:

Gastroeneritus – Causes diarrhea, nausea, vomiting, fever, and abdominal pain.

Cryptosporidiosis – Causes flu-like symptoms, diarrhea, weight loss, bloating, and nausea.

Water pollution can be defined as alteration in physical, chemical or biological characteristics of water, making it unsuitable for designated best use in its natural state.  

World Health Organization (WHO) has defined water pollution as inclusion of any foreign material either from natural or other sources into a water body, thereby changing the natural qualities of water and making it unusable for its intended purpose.

Industrial pollution contaminates many sources of drinking water, releases unwanted toxins into the air and reduces the quality of soil all over the world. Major environmental disasters have been caused due to industrial mishaps, which have yet to be brought under control. From the given options, electronics industry does not spread water pollution.

Dhebar lake (also known as Jaisamand lake) is Asia's second-largest artificial lake. It is located in the Udaipur District of Rajasthan state in western India. It has an area of 87 km when full, and was created in the 17th century when Rana Jai Singh of Udaipur built a marble dam across the Gomati River.

The Gadsisar Lake is one of the most famous tourist places in Jaisalmer which was built by Raja Rawal Jaisal, the first ruler of Jaisalmer. In the later years Maharaja Garisisar Singh rebuilt and revamped the lake. This historic lake is located towards the south of Jaisalmer city. The bank of the Gadsisar lake is surrounded by artistically carved Chattris, Temples, Shrines, and Ghats. Its charm lies in the fact that it was the only source of water for the Jaisalmer city in the olden days.

With a growing population comes a growing demand for water from the three main sectors of agriculture, around 70 percent, industry, around 22 percent and domestic use, around 8 percent. This increase in demand will cause a shortfall of almost 2000 megaliters of water by 2030.

Dryland communities have also developed deep knowledge of water and its elements. From the name of a particular system,(eg. a nadi) people knew how the water is collected, catchment prepared, embankment constructed, etc. Diverse systems to suit local ecology, geology, climate: nadi, talab, johad, bandha, etc. So many kinds of wells: Dugwells: kua owned by individuals; kohars community wells. Step wells: Baolis for drinking; constructed for philanthropic purposes; jhalaras not used for drinking. Different in architecture, Sagar ka kua : never run dry, Seer ka kua: underground channel opening into a well..

A rift valley is formed mainly due to the subsidence of the floor of a river valley. A rift valley is formed on a divergent plate boundary, a crustal extension or spreading apart of the surface, which is subsequently further deepened by the forces of erosion.

Human activities have been the major causes for the depletion of flora and fauna. Various such activities are –

1. Agricultural expansion

2. Shifting cultivation (Jhum), a type of ‘slash and burn’ agriculture.

3. Large scale development projects.

4. Mining activities.

5. Habitat destruction, hunting, poaching, over-exploitation of forest products, environmental degradation, forest-fire are some other factors which have led to the decline of India’s biodiversity.

6. Environmental destruction due to unequal access, inequitable consumption of resources and differential sharing of responsibilities for environmental well-being are also responsible for the depletion of flora and fauna.

The Indian Ocean is the only ocean named after a country, that is, India. The shape of the ocean is almost triangular. In the north, it is bound by Asia, in the west by Africa and the east by Australia. The Indian landmass has a central location between the East and West Asia. India is a southward extension of the Asian continent. The trans-Indian Ocean routes, which connect the countries of Europe in the West and the countries of East Asia, provide a strategic central location to India. No other country has a long coastline on the Indian Ocean as India has and indeed, it is India’s eminent position in the Indian Ocean, which justifies the naming of an Ocean after it.

There are reserves of a variety of natural resources in seawater, at the bottom of the sea and beneath the seabed, too. These resources available from seas and oceans are called marine resources.

Destination Fiji, a virtual guide to the island group in the South Pacific Ocean about 3,000 km north-east of Australia and 2,000 km north of New Zealand.

Its average depth is about 3,688 meters (12,100 ft), and its maximum depth is 10,994 meters (6.831 mi) at the Mariana Trench. Nearly half of the world's marine waters are over 3,000 meters (9,800 ft) deep. The vast expanses of deep ocean (anything below 200 meters or 660 feet) cover about 66% of Earth's surface.

Ionian Sea, Latin Mare Ionium, Italian Mare Ionio, part of the Mediterranean Sea, lying between Albania (northeast), Greece (east), Sicily (southwest), and Italy (west and northwest). Though considered by ancient authors to be part of the Adriatic Sea, the Ionian Sea is now seen as a separate body of water.

In general terms, Asia is bounded on the east by the Pacific Ocean, on the south by the Indian Ocean, and on the north by the Arctic Ocean. As no seas are bounded in asia.

The upper flow leaves the Black Sea and carries surface water out of it. Meanwhile a bottom flow carries salt water, about 35‰ from the Mediterranean to the Black Sea. The salty water mixes with the waters of the basin proper and that results in a comparatively low salinity at the surface, about 17%.

Valparaíso is located about 120 kilometres (75 mi) northwest of Santiago by road and is one of the South Pacific's most important seaports. Valparaíso is the capital of Chile's second most populated administrative region and has been the headquarters for the Chilean National Congress since 1990.

The prefix 'iso' is a greek word meaning equal, so an isoline must be a line joining equal points. For example, a line drawn on a map to join up all the places that are the same height above sea level is called a contour.