Runoff: Surface and Overland Water Runoff

When rain falls onto the earth, it just doesn’t sit there, it starts moving according to the laws of gravity. A portion of the precipitation seeps into the ground to replenish Earth’s groundwater. Most of it flows downhill as runoff. Runoff is extremely important in that not only does it keep rivers and lakes full of water, but it also changes the landscape by the action of erosion. Flowing water has tremendous power it can move boulders and carve out canyons; check out the Grand Canyon!

Runoff of course occurs during storms, and much more water flows in rivers (and as runoff) during storms. For example, in 2001 during a major storm at Peachtree Creek in Atlanta, Georgia, the amount of water that flowed in the river in one day was 7 percent of all the streamflow for the year.

Some definitions of runoff:.                               

1. That part of the precipitation, snow melt, or irrigation water that appears in uncontrolled (not regulated by a dam upstream) surface streams, rivers, drains or sewers. Runoff may be classified according to speed of appearance after rainfall or melting snow as direct runoff or base runoff, and according to source as surface runoff, storm interflow, or groundwater runoff.

2. The sum of total discharges described in (1), above, during a specified period of time.

3. The depth to which a watershed (drainage area) would be covered if all of the runoff for a given period of time were uniformly distributed over it.

Meteorological factors affecting runoff:

Type of precipitation (rain, snow, sleet, etc.)
* Rainfall intensity
* Rainfall amount
* Rainfall duration
* Distribution of rainfall over the watersheds
* Direction of storm movement
Antecedent precipitation and resulting soil moisture
*Other meteorological and climatic conditions that affect evapotranspiration, such as temperature, wind, relative humidity, and season.


Physical characteristics affecting runoff:

* Land use
* Vegetation
* Soil type
* Drainage area
* Basin shape
* Elevation
* Slope
* Topography
* Direction of orientation
* Drainage network patterns
* Ponds, lakes, reservoirs, sinks, etc. in the basin, which prevent or alter runoff from continuing downstream


Runoff and water quality :

A significant portion of rainfall in forested watersheds is absorbed into soils (infiltration), is stored as groundwater, and is slowly discharged to streams through seeps and springs. Flooding is less significant in these more natural conditions because some of the runoff during a storm is absorbed into the ground, thus lessening the amount of runoff into a stream during the storm.

As watersheds are urbanized, much of the vegetation is replaced by impervious surfaces, thus reducing the area where infiltration to groundwater can occur. Thus, more stormwater runoff occurs—runoff that must be collected by extensive drainage systems that combine curbs, storm sewers (as shown in this picture), and ditches to carry stormwater runoff directly to streams. More simply, in a developed watershed, much more water arrives into a stream much more quickly, resulting in an increased likelihood of more frequent and more severe flooding.

What if the street you live on had only a curb built around it, with no stormwater intake such as the one pictured here. Any low points in your street would collect water when it rained. And if your street was surrounded by houses with yards sloping uphill, then all the runoff from those yards and driveways would collect in a lake at the bottom of the street.

A storm sewer intake such as the one in this picture is a common site on almost all streets. Rainfall runoff, and sometimes small kids’ toys left out in the rain, are collected by these drains and the water is delivered via the street curb or drainage ditch alongside the street to the storm-sewer drain to pipes that help to move runoff to nearby creeks and streams. ; storm sewers help to prevent flooding on neighborhood streets.

Drainage ditches to carry stormwater runoff to storage ponds are often built to hold runoff and collect excess sediment in order to keep it out of streams.

Runoff from agricultural land (and even our own yards) can carry excess nutrients, such as nitrogen and phosphorus into streams, lakes, and groundwater supplies. These excess nutrients have the potential to degrade water quality.

Why might stormwater runoff be a problem?

As it flows over the land surface, stormwater picks up potential pollutants that may include sediment, nutrients (from lawn fertilizers), bacteria (from animal and human waste), pesticides (from lawn and garden chemicals), metals (from rooftops and roadways), and petroleum by-products (from leaking vehicles). Pollution originating over a large land area without a single point of origin and generally carried by stormwater is considered non-point pollution. In contrast, point sources of pollution originate from a single point, such as a municipal or industrial discharge pipe. Polluted stormwater runoff can be harmful to plants, animals, and people.

Runoff can carry a lot of sediment

When storms hit and streamflows increase, the sediment moved into the river by runoff can end up being seen from hundreds of miles up by satellites. The right-side pictures shows the aftermath of Hurricane Irene in Florida in October 1999. Sediment-filled rivers are dumping tremendous amounts of suspended sediment into the Atlantic Ocean. The sediment being dumped into the oceans has an effect on the ecology of the oceans, both in a good and bad way. And, this is one of the ways that the oceans have become what they are: salty.

Florida, Oct. 14, 1999. When Hurricane Irene passed over Florida in 1999, the heavy rainfall over land caused extensive amounts of runoff that first entered Florida’s rivers which then dumped the runoff water, containing lots of sediment, into the Atlantic Ocean.

Florida, Dec. 16, 2002. The east coast of Florida is mostly clear of sediment from runoff. The shallow coastal waters to the west of Florida are very turbid (sediment-filled), perhaps from a storm that passed over a few days earlier.

The end.….

CHANDRAYAAN-1India’s First Lunar Exploration Mission. Moon Mineralogy Mapper observations point to possibility of water on the Moon!

Chandrayaan-1, India’s first mission to Moon, was launched successfully on October 22, 2008 from SDSC SHAR, Sriharikota. The spacecraft was orbiting around the Moon at a height of 100 km from the lunar surface for chemical, mineralogical and photo-geologic mapping of the Moon. The spacecraft carried 11 scientific instruments built in India, USA, UK, Germany, Sweden and Bulgaria.



After the successful completion of all the major mission objectives, the orbit has been raised to 200 km during May 2009. The satellite made more than 3400 orbits around the moon and the mission was concluded when the communication with the spacecraft was lost on August 29, 2009.

The idea of undertaking an Indian scientific mission to Moon was initially mooted in a meeting of the Indian Academy of Sciences in 1999 that was followed up by discussions in the Astronautical Society of India in 2000.

Based on the recommendations made by the learned members of these forums, a National Lunar Mission Task Force was constituted by the Indian Space Research Organisation (ISRO). Leading Indian scientists and technologists participated in the deliberations of the Task Force that provided an assessment on the feasibility of an Indian Mission to the Moon as well as dwelt on the focus of such a mission and its possible configuration.

After detailed discussions, it was unanimously recommended that India should undertake the Mission to Moon, particularly in view of the renewed international interest in moon with several exciting missions planned for the new millennium. In addition, such a mission could provide the needed thrust to basic science and engineering research in the country including new challenges to ISRO to go beyond the Geostationary Orbit. Further, such a project could also help bringing in young talents to the arena of fundamental research. The academia would also find participation in such a project intellectually rewarding.

Subsequently, Government of India approved ISRO’s proposal for the first Indian Moon Mission, called Chandrayaan-1 in November 2003.

The Chandrayaan-1 mission performed high-resolution remote sensing of the moon in visible, near infrared (NIR), low energy X-rays and high-energy X-ray regions. One of the objectives was to prepare a three-dimensional atlas (with high spatial and altitude resolution) of both near and far side of the moon. It aimed at conducting chemical and mineralogical mapping of the entire lunar surface for distribution of mineral and chemical elements such as Magnesium, Aluminium, Silicon, Calcium, Iron and Titanium as well as high atomic number elements such as Radon, Uranium & Thorium with high spatial resolution.

Various mission planning and management objectives were also met. The mission goal of harnessing the science payloads, lunar craft and the launch vehicle with suitable ground support systems including Deep Space Network (DSN) station were realised, which were helpful for future explorations like the Mars Orbiter Mission. Mission goals like spacecraft integration and testing, launching and achieving lunar polar orbit of about 100 km, in-orbit operation of experiments, communication/ telecommand, telemetry data reception, quick look data and archival for scientific utilisation by scientists were also met.

PSLV-C11
PSLV-C11, chosen to launch Chandrayaan-1 spacecraft, was an updated version of ISRO’s Polar Satellite Launch Vehicle standard configuration. Weighing 320 tonne at lift-off, the vehicle used larger strap-on motors (PSOM-XL) to achieve higher payload capability.

PSLV is the trusted workhorse launch Vehicle of ISRO. During September 1993- April 2008 period, PSLV had twelve consecutively successful launches carrying satellites to Sun Synchronous, Low Earth and Geosynchronous Transfer Orbits. On October 22, 2008, its fourteenth flight launched Chandrayaan-1 spacecraft.

By mid 2008, PSLV had repeatedly proved its reliability and versatility by launching 29 satellites into a variety of orbits. Of these, ten remote sensing satellites of India, an Indian satellite for amateur radio communications, a recoverable Space Capsule (SRE-1) and fourteen satellites from abroad were put into polar Sun Synchronous Orbits (SSO) of 550-820 km heights. Besides, PSLV has launched two satellites from abroad into Low Earth Orbits of low or medium inclinations. This apart, PSLV has launched KALPANA-1, a weather satellite of India, into Geosynchronous Transfer Orbit (GTO).

PSLV was initially designed by ISRO to place 1,000 kg class Indian Remote Sensing (IRS) satellites into 900 km polar SunSynchronous Orbits. Since the first successful flight in October 1994, the capability of PSLV was successively enhanced from 850 kg to 1,600 kg. In its ninth flight on May 5, 2005 from the Second Launch Pad (SLP), PSLV launched ISRO’s remote sensing satellite,1,560 kg CARTOSAT-1 and the 42 kg Amateur Radio satellite, HAMSAT, into a 620 km polar Sun Synchronous Orbit. The improvement in the capability over successive flights has been achieved through several means. They include increased propellant loading in the stage motors, employing composite material for the satellite mounting structure and changing the sequence of firing of the strap-on motors.

Vikram Sarabhai Space Centre (VSSC), Thiruvananthapuram, designed and developed PSLV-C11. ISRO Inertial Systems Unit (IISU) at Thiruvananthapuram developed the inertial systems for the vehicle. Liquid Propulsion Systems Centre (LPSC), also at Thiruvananthapuram, developed the liquid propulsion stages for the second and fourth stages of PSLV-C11 as well as reaction control systems. SDSC SHAR processed the solid motors and carries out launch operations. ISRO Telemetry, Tracking and Command Network (ISTRAC) provide telemetry, tracking and command support during PSLV-C11’s flight

Who can submit a Proposal?

Proposals could be submitted by individuals or a group of scientists and academicians belonging to recognized institutions, universities, planetaria and government organisations of India. Only those having at least a minimum remaining service of four years before superannuation are eligible to lead the project as PI/Co-PI. The proposals must be forwarded through the Head of the Institution, with appropriate assurance for providing necessary facilities for carrying out the projects under this AO programme. The end….