6 Basin Hydrology

Objectives

To make the reader understand the concept of river basins and hydrology.

Keywords

Hydrology, Basin, Hydrologists, Reservoirs, Catchment area, Traversing, Topography, Hazards, Drainage basins, Pollutants, Solute, Watershed, Downhill, Uphill, Ganga, Brahmaputra, Indus, Godavari, Krishna, Cauvery, Luni, Gandhak.

    Water is one of our most important natural resources. The lack of water may result in the absence of life on the Earth. The amount of water available for our use is limited by nature. Water resources on the earth are plenty in number however; it is not always in the right place, at the right time and of the right quality fit for consumption and it has to go through several purification processes to make it fit for consumption. It is sometimes very difficult and expensive to obtain clean drinking water in many parts of the world where strikingly, the cost of a liter of drinking water is more expensive than any other commodity of daily use. In addition to the scarcity of water, we face another major problem which is the problem of the increasing pollution in the form of chemical wastes being discarded carelessly for years are showing up in our water supplies today. Our major rivers are highly polluted and the result is that the aquatic life is dying and we are suffering from several water borne diseases as a result of consuming highly intoxicated water obtained from our rivers.

Hydrology is the scientific study of the movement, distribution, and quality of water on the Earth’s surface; the water cycle, the water resources and environmental watershed sustainability are the integral part of the study of hydrology. A Hydrologist is a student who studies or practices hydrology. He has a very crucial task to perform as he may be may be working within the fields of Environmental Sciences or pursuing or working in the study of Earth Sciences, he may be working or researching in the field of Physical Geography as a

Physical Geographer, he may also be working in the field of Geology or Civil and Environmental Engineering. Using various analytical methods and scientific techniques, a Hydrologist can collect and analyze data to help solve water related problems concerned with serious issues such as those of the nature of environment conservation, natural disasters and their management, and management of water and water bodies on the Earth.

Hydrology has gradually evolved as a science discipline. It is a very significant study and the need of the study arose so as to facilitate the learning and to understand the vast and highly complex network of water systems on the surface of the Earth and also to help to resolve water related problems being faced by all living beings be it plants, animals or humans. Hydrologists play a crucial and vital role in finding solutions to water related problems. In the modern world, interesting and challenging career options are available for those who choose to study hydrology.

Much of our water we consume is actually in a hidden form. Think about what you had for lunch. A piece of chapatti, for example, requires water to grow wheat for the same, and the process of making the chapatti requires water to knead the dough. When we consume the chapatti, we also eat some vegetable for which again we require water to grow and then wash and cook the particular vegetable. This all-Indian meal uses about a thousand liters of water –enough to fill a small swimming pool. How about your clothes? To grow cotton for a pair of jeans takes about 400 gallons of water. A shirt requires about 400 gallons. How do you get to school or to the store? To produce the amount of finished steel in a car has in the past required about 32,000 gallons of water. Similarly, the steel in a 30-pound bicycle required 480 gallons. This shows that industry must continue to strive to reduce water use through technology and manufacturing processes that use less water and through the study of Hydrology which is also the science that encompasses the occurrence, distribution, movement and properties of the waters of the earth and their relationship with the environment within each phase of the hydrologic cycle.

The water cycle, or hydrological cycle, is a continuous process by which water is purified by evaporation and transported from the earth’s surface (including the oceans) to the atmosphere and back to the land and oceans. All of the physical, chemical and biological processes involving water as it travels its various paths in the atmosphere, over and beneath the earth’s surface and through growing plants, are of interest to those who study the hydrological cycle. There are many pathways the water may take in its continuous cycle of falling as rainfall or snowfall and returning to the atmosphere. It may be captured for millions of years in polar ice caps. It may flow to rivers and finally to the sea. It may soak into the soil to be evaporated directly from the soil surface as it dries or be transpired by growing plants. It may percolate through the soil to ground water reservoirs (aquifers) to be stored or it may flow to wells or springs or back to streams by seepage. The cycle for water may be short, or it may take millions of years. People tap the water cycle for their own uses. Water is diverted temporarily from one part of the cycle by pumping it from the ground or drawing it from a river or lake. It is used for a variety of activities such as households, businesses and industries; for irrigation of farms and parklands; and for production of electric power. After use, water is returned to another part of the cycle: perhaps discharged downstream or allowed to soak into the ground. Used water normally is lower in quality, even after treatment, which often poses a problem for downstream users. The hydrologist studies the fundamental transport processes to be able to describe the quantity and quality of water as it moves through the cycle (evaporation, precipitation, stream flow, infiltration, ground water flow, and other components). The engineering hydrologist, or water resources engineer, is involved in the planning, analysis, design, construction and operation of projects for the control, utilization, and management of water resources. Water resources problems are also the concern of meteorologists, oceanographers, geologists, chemists, physicists, biologists, economists, and political scientists, specialists in applied mathematics and computer science, and engineers in several fields.

Hydrology subdivides into surface water   hydrology,  groundwater hydrology (hydrogeology), and marine hydrology. Domains of hydrology include hydrometeorology, surface hydrology, hydrogeology, drainage-basin management and water quality, where water plays the central role.

Oceanography and meteorology are not a part of the discipline because water is only one of many important aspects within those fields.

Hydrological research can inform environmental engineering, policy and planning. Hydrological research is carried out by hydrologists. Let us now look at what hydrologists do.

What Hydrologists Do?

Hydrologists apply scientific knowledge and mathematical principles to solve water-related problems in society: problems of quantity, quality and availability. They may be concerned with finding water supplies for cities or irrigated farms, or controlling river flooding or soil erosion. Or, they may work in environmental protection: preventing or cleaning up pollution or locating sites for safe disposal of hazardous wastes. Persons trained in hydrology may have a wide variety of job titles. Scientists and engineers in hydrology may be involved in both field investigations and office work. In the field, they may collect basic data; oversee testing of water quality, direct field crews and work with equipment. Many jobs require travel, some abroad. A hydrologist may spend considerable time doing field work in remote and rugged terrain. In the office, hydrologists do many things such as interpreting hydrologic data and performing analyses for determining possible water supplies. Much of their work relies on computers for organizing, summarizing and analyzing masses of data, and for modeling studies such as the prediction of flooding and the consequences of reservoir releases or the effect of leaking underground oil storage tanks. The work of hydrologists is as varied as the uses of water and may range from planning multimillion dollar interstate water projects to advising homeowners about backyard drainage problems. Surface Water

All settlements require water and so most of the settlements are found along the rivers, lake or reservoirs. The duties of the Hydrologists include helping the cities by collecting and analyzing the data needed to predict how much water is available currently from the local supplies and whether it will be sufficient to meet the city’s projected future needs. This requires the hydrologists to study the records of rainfall for a selected time period, the depths of the rivers and river flows, the amount of water being collected by the process of melting of the glaciers and snow etc. The data then obtained is collected and compiled by the hydrologists working in various government agencies. Managing and maintaining the reservoirs can be quite a complex task because reservoirs are generally multipurpose in nature. With the construction of Reservoirs there is an increase in the local water supplies. Hydrologists use topographic maps and aerial photographs and very recently have also started using drones to determine where the shorelines of the reservoirs could be and also to calculate the reservoir depths and their storage capacity. This ensures that, even when the reservoir is at its maximum capacity, no highways, railroads or homes would be flooded.

Groundwater

Groundwater, which is obtained by pumping from beneath the earth’s surface, is often definitely cheaper, more convenient and less vulnerable to pollution than the surface water. Therefore, it is very commonly used for public water supplies. Groundwater provides the largest source of usable water storage in the United States whereas, in India it is not very economical to obtain groundwater easily as the process of installing a water pump is a tedious and expensive task. Underground reservoirs contain far more water than the capacity of all surface reservoirs and lakes. Most of the water being used in India is obtained from the rivers. This water is purified in special plants and then supplied to the cities. In the rural parts of the country, the people still depend on wells, tube wells and in many parts of the country, especially in the desert or the arid regions, a very common sight is women carrying vessels and going to the nearby streams or rivers to collect water.

Hydrologists estimate the volume of water stored underground by measuring water levels in local wells and by examining geological records from well-drilling to determine the extent, depth and thickness of water-bearing sediments and rocks. Before the construction of a well or reservoir, a hydrologist performs a survey through field research. Test wells are drilled under the expert guidance of hydrologists and once the results of the test wells are satisfactory, the actual wells are drilled in order to facilitate the supply of water for the local settlements. It is a part of the hydrologist’s job to note the depths at which water is found and they collect samples of soils, rock and water for laboratory analyses. They may run various geophysical tests on the completed well, keeping an accurate log of their observations and test results. Hydrologists determine the most efficient pumping rate by monitoring the extent that water levels drop in the pumped well and in its nearest neighbors. Pumping the well too fast could cause it to go dry or could interfere with neighboring wells. Over pumping along the sea coasts can cause salt water intrusion in the wells resulting in the water being obtained to be salty in taste. By plotting and analyzing this data, hydrologists can estimate the maximum and optimum yields of the wells.

Branches of hydrology

The following are the branches of hydrology.

    Ø Chemical hydrology- The study of the chemical characteristics of water is known as chemical hydrology.

Ø  Eco-hydrology is the study of interactions between living organisms be it plants or animals and the hydrologic cycle.

Ø  Hydrogeology is the study of the presence and the movement of groundwater.

Ø Hydro informatics is the adaptation of information technology to hydrology and water resources applications.

Ø Hydrometeorology is the study of the transfer of water and energy between land and water body surfaces and the lower atmosphere.

Ø Isotope hydrology is the study of the isotopic signatures of water.

Ø Surface hydrology is the study of hydrologic processes that operate at or near Earth’s surface.

Ø Drainage basin management covers water-storage, in the form of reservoirs, and flood-protection.

Ø Water quality includes the chemistry of water in rivers and lakes, both of pollutants and natural solutes.

Hydrological processes within a river basin Drainage basins of India

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Drainage Basin

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Each stream or river has its own drainage basin; a larger river system is made up of all of the smaller streams and their respective drainage basins. Small streams flow into larger streams, then rivers and finally, into the open bodies of water such as the oceans, bays or seas. The drainage basin of a larger river system is made up of many branch like networks which strikingly resemble like the branches of a tree. It starts at high elevation with first-order streams, which are small streams that originate from springs. First-order streams are where the system begins, and they do not have any other streams flowing into them.

Next, there are second-order streams, which are streams that are created when two first-order streams meet. These streams are slightly larger and more downhill from first-order streams. When two second-order streams meet, they create a third-order stream. This process can continue until a large network of waterways is created. All of the branches of the system will eventually come together and lead to the final large waterway that will empty into the open body of water.

The drainage basin for this entire river system would be very large and incorporate each drainage basin from individual waterways. These systems can be very complex. We can think of it as a tree with many branches. The smaller, twig-like branches lead to larger branches, and finally they all meet at the trunk of the tree.

Definition of a drainage basin (also often known as: a watershed, river basin, or catchment area): A river basin or a drainage basin is an area of land drained by a river system, including its tributaries and distributaries as a complete network. The edge of the drainage basin is known as the watershed. This can be compared to a sink or basin, which holds the water falling into it.

It is widely accepted as the natural unit of water management worldwide and it is the epicenter for the scientific study of hydrological processes. The demarcation of these river basins is also a very crucial yet important task taken up by the hydrologists. The demarcation is mainly for the planning and the development of the water existing resources and also for the ones which can be tapped for the near future. According to a report by the Central Water Commission, there are twenty two huge river basins in India. These river basins have been classified by the various organizations such as India WRIS (Water Resource Information System) basin, NCIWRDP (National Commission for Integrated Water Resource Development Plan) basin, AISLUS (All India Soil and Land use Survey) basin, CGWB (Central Groundwater Board) basin. The map given below shows the twenty two river basins of India classified by the CWC.

River basins of India as classified by CWC (Source India WRICS)

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The ten largest river basins in India are:

The Ganga Basin– the length of the Ganga Basin is 861452 sq. km making it the longest basin in India. The river originates from the Gangotri Glacier in the Himalayas and traverses about 2,525 kilometers across the North Indian states of Uttar Pradesh, Bihar, Uttrakhand, Jharkhand and West- Bengal. All these states have a large population and the River Ganga caters to the water needs of the large population. The most important tributaries of the river are Yamuna, Chambal, Banas, Kali Sindh, Parbati, Sindh, Betwa, Dhasan, Kheri, Gomti, Sarda, Ghagra, Gandhak, Son, Damodar, Ramganga, Mahananda and Hoogly.

   Taken from CWC

West flowing rivers of the Saurashtra and Kutch and Luni– the length of this river basin is 321851 sq km. This basin has many independent rivers such as the Luni, Shetrunji, Bhadar, Machhu, Rupen, Saraswati and Banas. Luni is the major river system of this particular basin. The Western Slopes of the Aravallis is the origin of Luni which falls under the Ajmer district of Rajasthan. The river traverses a distance of 511 kilometers before it enters into the Arabian Sea. The main tributaries of Luni are Lirli, Guhiya, Bandi, Sukri, Jawai, Khari Bandi, Sukri Bandi, Sagi and Jojri.

   Taken from CWC

The Indus Basin– the basin covers an area of 321289 sq km. The origin of the river is around the Mansarovar Lake in the upper Himalayan mountain region. It drains a total area of 2880 kilometers (Including India and Pakistan) before it enters into the Arabian Sea. The Indian part of the river flows through the state of Jammu and Kashmir and it flows through a total length of 1114 kilometers. The main tributaries of Indus are Shyok, Jhelum, Ravi, Beas, Chenab, Satluj and Ghaggar.

The map below taken from CWC shows the basin clearly.

   Taken from CWC

The Godavari Basin– the river Godavari originates from Thrimbakeshwar in the Nashik district of the state of Maharashtra. The length of the river is 1465 km. the river flows through and drains the states of Maharashtra, Telangana and Andhra Pradesh. The water it receives is through a basin which covers an area of 312812 sq km. It commences its journey into the Bay of Bengal. The main tributaries of Godavari are Pravara, Manjra, Purna, Penganga, Wardha, Wainganga, Indravati and Kolab.

   Taken from CWC

The Krishna River Basin– it covers an area of 258948 sq km. the main river is the Krishna River which originates from the Jor Village in the Satara district of the state of Maharashtra. The total length of the river is 1400 km long and it flows through the states of Maharashtra, Karnataka, Telangana and Andhra Pradesh. This river also finally enters into the Bay of Bengal. The most important tributaries of Krishna are, Ghatprabha, Malprabha, Tungbhadra, Musi, Bhima and Munneru.

   Taken from CWC

The Brahmaputra River Basin– 194413 sq km is the total area covered by this basin. The total length of the Brahmaputra is 2900 kilometers. The area that the river covers in India is only 916 kilometers. The states of Assam and Arunachal Pradesh are fed by this river. The river originates from the Kailash ranges south of the lake Konggyu Tsho. The principal tributaries of the Brahmaputra include Lohit, Dibang, Subansiri, Jiabharali, Dhansiri, Manas, Torsa, Sankosh, Teesta, Burhidihing, Disang, Dikhow and Kopili.

Taken from CWC

The Mahandi River Basin– this river basin spreads over five highly populated states of the country. The total area covered by this basin is 141589 sq km. the five states that this basin covers are Chattisgarh, Odisha, Madhya Pradesh, Jharkhand and Maharashtra. Most of the areas covered by this basin lie in Chattisgarh and Odisha. This river originates in the Farsiya village of the district Dhamtari of the state of Chattisgarh. It traverses 851 km in the states of Chattisgarh and Odisha and finally falls into the Bay of Bengal. The main tributaries are Sheonath, Hasdeo, Mand, Ib, Ong, Tel and Jonk.

Taken from CWC

Basin of the East Flowing Rivers– this river basin has two river systems. The river system between the rivers Pennar and Cauvery and also between the rivers Cauvery and Kannyakumari. The total area being covered by this drainage system is 100139 sq km and it also includes many independent rivers such as Kandleru, Swaranmukhi, Arani, Kortalaiyar, Coom, Adyar, Palar, Gingee, Ponnalyar, Vellar, Varshalei, Valgai, Gundar, Vaippar and Tambraparni rivers. All these rivers end their journey into the Bay of Bengal.

   Taken from CWC

    The Narmada River basin– the total area covered by this basin is 98796 sq km. This river system covers the states of Madhya Pradesh, Gujarat, Chhattisgarh and Maharashtra. This river originates from the Maikala range in Amarkantak in the Annuppur district of the state of Madhya Pradesh. The main tributaries of Narmada are Bhurner, Banjar, Sher, Shakkar, Dudhi, Tawa, Ganjal, Kundi, Gol, Karjan, Tendoni, Barna, Kolar, Man, Uri, Hatni and Orsang.

Taken from CWC

Basin of the East flowing rivers– these rivers flow between Mahanadi and Pennar. This region witnesses three river systems. One being between Mahanadi and Godavari, the second one being the river system between Krishna and Pennar and the third one being between Godavari and the Krishna rivers which is a small yet significant one. This is drained by mainly a small stream named Palleru. The total

area that is significantly covered by this basin is 86643 sq km. This basin also strikingly has many independent rivers which flow into the Bay of Bengal. These rivers are Rushikulya, Bhadua, Vamsadhara, Nagavali, Sarada, Varaha, Eluru, Tandava, Gundalakamma, Musi, Paleru and Manneru.

The size of any basin depends on the amount of water being carried by each stream which forms that basin. There are several river basins which depend mainly on the rainwater hence; they’re almost dry during the year and during the rainy season, their size increases as there is a good amount of water flow in the streams. There are many other significant basins in the country and their existence is crucial for the large population and settlements depending on them for their daily activities, industries, agriculture etc. India being an agriculture based economy is wholly dependent on the availability of water to perform agricultural activities because the lack of water would mean poor crop cultivation which would result in a great loss to the economy.

Surface runoff- (also known as overland flow) is described as the excess flow of water that takes place when storm water, melting water from glaciers, or water from other sources flows over the Earth’s surface. This might occur when the soil is unable to absorb the full capacity of the sudden water flow, because rain arrives more quickly than soil can absorb it, or also because the areas which are concrete in nature such as pavements or the roofs of houses send their excess water (runoff) to the surrounding soft ground that cannot absorb all of the sudden extra water flow. Surface runoff is a major component of the water cycle. It is the primary agent in soil erosion by water.

Surface Runoff on a farmland—Note the soil being eroded due to runoff

 Evapotranspiration- (ET) is the total amount of evaporation and the transpiration from the flora and fauna from the land and ocean surface to the atmosphere. Evaporation accounts for the movement of water to the air from sources such as the soil, canopy interception, and water bodies. Transpiration accounts for the movement of water within a plant and the subsequent loss of water as vapor through stomata in its leaves. Evapotranspiration is an important part of the water cycle. An element (such as a tree) that contributes to evapotranspiration can be called an evapotranspirator.

There may be groundwater flowing in or out of the system; an alternative approach to formulate the balance is: P+ET+Q+G=dS; P: precipitation, ET: Evapotranspiration, Q: discharge of river, G: Groundwater flow, dS: change in storage; fluxes in are positive, fluxes out are negative

Planting more trees or increasing the vegetative cover on the Earth could increase evaporation losses by up to 50 to 100%, extensive cutting of trees increases runoff stem flow (flow along the stem), through fall (the precip that has avoided interception or dripped off the canopy) interception has also an influence on water quality

Careers in Hydrology

Students who plan to become hydrologists should be good in subjects like mathematics, statistics, geology, physics, computer science, chemistry and biology. In addition, sufficient background in other subjects–economics, public finance, environmental law, government policy–is needed to communicate with experts in these fields and to understand the implications of their work on hydrology. Communicating clearly in writing and speech is a basic requirement essential for any professional person. Hydrologists should be able to work well with people, not only as part of a team with other scientists and engineers, but also in public relations, whether it be advising governmental leaders or informing the general public on water issues. Hydrology offers a variety of interesting and challenging career choices for today and tomorrow. It’s a field worth considering.

References

• Dingman, S.L. (1994) Physical Hydrology. Prentice Hall, Englewood Cliffs.
• De Barry, Paul A. (2004). Watersheds: Processes, Assessment and Management. John Wiley & Sons.
• Rosgen, Dave (1996). Applied River Morphology. 2nd Ed.
• Brice J C. Plan form properties of meandering rivers [C].River Meandering, Proceedings of the October 24–26, 1983 Rivers ’83 Conference, ASCE. New Orleans, Louisiana, 1983. 1-15.
• Suresh. R. (2008) Watershed Hydrology.
• Suresh. R. (1997) Watershed and Hydrology.
• Singh. V.P. (Editor), Sharma. Nayan (Editor), Shekhar. C. & Ojha.P (Editor) The Brahmaputra Basin Water Resources.
• Seethapathi. P.V.  and  Dutta. D. Hydrology of small Watersheds.

Websites

• http://www.indiawaterportal.org
• https://books.google.co.in – Reddy. Jaya. Rami. A textbook of Hydrolog
• http://www.cwc.nic.in