School Students

People have used waterways as a mode of transport for hundreds of years. Aquatic ecosystems are being severely altered or destroyed at a rate greater than that at any other time in human history and faster than they are being restored. Pollutants from industries, agricultural lands, wastewater (superheated) from power stations, draining of sewage into aquatic ecosystems have led to eutrophication, which in turn has greatly affected the aquatic habitat.

The term “restoration' means the re-establishment of pre-disturbance of aquatic functions and is related physical, chemical and biological characteristics. Restoration aims to return an ecosystem to a natural condition. The relationship or interaction between the biotic community and abiotic environment needs to be restored. All the ecosystems of the earth are inter-related and they need to function as a single large self-sustaining biological system so that the functional stability is restored.

I have seen the Hebbal lake, from my younger days that was once filled with water hyacinth. Now through the Norwegian technology, a part of it is restored.

I foresee the possibility of “Bioengineering” as a technological method in aquatic ecosystem restoration (as seen in other parts of the world) apart from other proposed methods or recommendations.

Only about 3% of all water on Earth is fresh, the rest is salty. Yet this fresh water supports an amazing variety of life, whether it is in flowing streams and rivers or still ponds and lakes. The wetlands around the pond or a lake are also the homes for many plants, insects and birds.

The chemical nature of water in a pond or a lake depends upon the balance of them all and far their degradation, human beings have been responsible. Eutrophication is caused due to too much of chemicals drained off by farmlands, or by sewage. Algal growth can get out of control, creating an unpleasant green scum. This affects light penetration from reaching under water plants and the algal bloom dies and rots, a biological oxygen demand is created that kill aquatic organisms.

The pond or the lake could turn into woodlands by a natural process termed succession, as shallow ponds are themselves short-lived in nature.

In 1992 the UNO called for the Earth Summit at Rio-de-Janerio in Brazil to protect Biodiversity.

It has been defined as the return of an ecosystem to a close approximation of its condition prior to disturbance. In restoration, both the structure and the functions of the ecosystem are recreated. Restoration needs to bring in natural, self-sustaining and self-regulating entities.

Another definition for restoration - it means the re-establishment of pre disturbance of aquatic functions and related physical, chemical and biological characteristics (Cairns, 1998; Magnuson et. al, 1980; Lewis, 1989).

In this regard Lake 2000 has already put forth their strategies and recommendations.

Agencies for effective implementation of activities related to restoration of wetlands, their sustainable utilization & conservation.

Recommendation 2 - to set up a National committee for lakes and wetlands reclamation, restoration and development to formulate a national policy to evolve strategies for their sustainable utilization and conservation.

Recommendation 3 - student's involvement including curriculum development concerning the protection of the ecosystem and so on.

One of the restoration techniques, which I would like to speak on, is the use of Bioengineering.

Eg: The bioengineering techniques used in Germany for erosion control includes a relatively low-cost biodegrades breakwater with wetlands located shoreward. The technique has application for shoreline erosion control on many US reservoirs with dense thickets of young, woody trees, eg. Willows, cottonwood and alder, located near them since these materials are used in the breakwater. In Germany, the technique has only been applied where water levels do not fluctuate more than 1m, the technique was adapted from a method used to regain land lost to the northern sea along North German coastline. The technique was adapted for use in a demonstration study on the Havel Lake in Berlin 8 years ago. The wetlands were being gradually destroyed to various reasons, choking out by drifting garbage, discharge of toxins and contamination of water by oi, heavy metals, etc. to name a few.

Bioengineering Technique Used:

Is a combination of breakwater planted wetlands shoreward of the breakwater. Wetland plants are often grown in a Coconut fibre substrate in one of the following forms: Fibre Pellets (80 by 125 cm); Coconut fibre vegetation carpets are rolled out onsite (0.5 to 2.0 m wide by 5m long); and 20-by-20 cm bulbs. All of these forms lend themselves to immediate transfer to the site and short-term shore stabilization until the vegetation becomes established. Wetlands are not usually planted the breakwater is in place.

In 1991, for this wetland system including the branch box breakwater, wetland plants installed as pallets and bulbs, coconut fibre filter fabric were between $400 to $460 per metre for a 10 to 20 m swath from the breakwater landward. Generally, costs of bioengineering are a fraction of the costs of traditional alternatives such as Riprap Armament. The construction cost is lower in Germany because of the existing equipment such as barge-mounted pneumatic hammers and shallow-draft barges and boats.

This technique permits effective, low-cost erosion control, without destroying shoreline habitat. In addition, the wetlands provide sediment entrapment, water quality improvement, aesthetic quality improvement, protection of cultural and archeological resources etc.

Bioengineering is a new innovative practice of integrating structural components with living plants and fibres to accomplish specific goals or tasks. These tasks include:

* Stablization of erosion-prone soils including shorelines, beaches, stream banks and other ecologically sensitive areas.

Typically Natural (plant) and artificial (biodegradable textile), fibre rolls, mats are securely anchored along critical stream bank areas and planted with selected wetland species. The introduced vegetation rapidly colonizes the planting medium with strong, dense roots, rhizomes and stems forming a near indestructible erosion proof barrier, biofilter or fish enhanced habitat. Bioengineering is a cost effective approach to saving many global environmental problems.

The use of bioengineering methods dates back to 12th century China, when brush bundles were used to stabilize slopes. In the early 20th century, similar techniques were used in China to control flooding and erosion along the Yellow River. In Europe, especially Germany, bioengineering methods have been used for over 150 years. Documented use of bioengineering in the United State dates to the 1920s and '30s. Stream bank stabilization, timber access road stabilization and slope restoration were common applications. After World War II, with increased access to earth-moving equipment and the development of new structural slope stabilization and erosion control methods, bioengineering practices all but disappeared. In the last 20 years bioengineering has been recognized as a re-emerging technique to provide erosion control, environmentally sound design and aesthetically pleasing structures.

Gray and Leiser (1982) published the first U.S. textbook on bioengineering:

Limitations to bioengineering methods include:

1) The installation season is often limited to plant dormant seasons, when site access may be limited;

3) Labor needs are intensive and skilled, experienced labor may not be available;

4) Installers may not be familiar with bioengineering principles and designs so upfront training may be required;

5) Alternative practices are aggressively marketed and often more widely accepted by society and contractors.

New methods of application and materials being developed will result in new and improved Bioengineering design.

This method is used to control surface erosion by breaking long slopes into shorter slopes. Bundles of branches, called wattles or fascines, are placed in shallow trenches along the slope or stream bank contour. Trenches are excavated by hand to half the diameter of the bundles. Wattles are typically 8 to 10 inches in diameter and branches secured with twine. After the wattle is staked in place, the trench is backfilled until only the top of the bundle is exposed. Wattles can be used for hill slope restoration, road embankments, wide gullies, or slump areas.

This methodis used to restore slopes by constructing a fill-slope consisting of alternating layers of live branches and soil, creating a series of reinforced benches. Large quantities of dormant willow branches are often used. While about 75 percent to 80 percent of the branch is buried, the tips are left exposed. The layers of branches help reinforce the fill, which improves as the branches develop roots throughout the fill area. Brush layering can be used to place new fill or repair old fill areas, restore shallow slumps, repair narrow gullies and stabilize loose soil slopes.

This method is used to slow or spread water by placing live plants in a trench perpendicular to the flow. To reduce wave impact, live plants are placed in trenches running parallel to the shoreline. Several trenches may be used with different plants in each, depending on the distance to water. Generally, a wide planting area is needed to dissipate wave energy. In upland areas, trench packing serves to slow water and spread it over the soil surface, reducing its erosion potential. Trench packing can also be used to control shallow seeps, protect wetland contruction and renovation and protect abandoned roads.

Live cuttings can be used to secure materials in place and to increase plantings on a slope. Live cutings can be from 18 inches to 4 feet in length. Longer cuttings are used for live staking of wattles, while shorter cuttings are used for plantings.

Staking:

Staking is used extensively in bioengineering practice. Stakes can be live or dead. Live staking is often done with willows to stabilize soil or to stake other materials in place. Manufactured timber stakes, 2 to 3 feet long, are used to securee wattles and coir fascines. Timber stakes for upland application need to have a bias, or angle, cut making them easier to install. For wetland or streamside applications, stakes need straight parallel sides to prevent heaving from water pressure.

This method protects stream-banks by placing a mattress-like layer of branches over it to protect soil and slow water velocity. The mat is composed of interwoven, usually dead, branches secured to the soil by live stakes, wire, twine or live branches. Live stakes are often cut from dormant willow. Brush matting helps collect sediment and enables establishment of vegetation on banks. Like bruch layering, this method requires large quantities of branches.

Combinations of the above practices are usually used for most bioengineering designs. For example, brush wattles and live staking is a common combination used to stabilize slopes. A coir fascine can be used with live plantings, brush matting and trench packing to restore wetlands or stream channels. New combinations of existing methods, and the use of new materials, will provide creative applications of bioengineering techniques.

Coir fascines are wattles made from fibrous outer husk of coconuts. Coir is denser than water so it won't float and is very slow to decay. Coir fascines are a readily available manufactured product and are popular for stream-bank and wetland restoration where a natural look is desired. Coir fascines are placed with their tops at the water surface. Live plants can be placed into coir fascines to create a natural look.

Status of Wetlands in Bangalore

Bangalore has no natural wetlands, they were built mainly for various hydrological purposes and mainly to serve the needs of irrigated agriculture. Prior to 1896, the water demand of the city was met by surface water-bodies and dug wells. The unplanned development of the city has engulfed many water bodies and also blocked these catchment basins. The number of man-made wetlands in the existing BCC and BDA area has fallen from 262 in 1960, to around 81 lakes at present. About 35% of the water bodies of Bangalore were lost in the past 20 years. Remaining lakes are on the verge of extinction, as they are filled with solid wastes and untreated sewage.

Experimental Procedure

The study concentrated on analysing the depth of the lake, computing its catchment yield and volume. The study also concentrated on the quality of lake water and ground water in the surrounding areas. Another component of this study was the evaluation of the economic dependency of the people living in the neighbouring areas of the lake, which gives an idea about the neccessity to restore the lake. After thorough analysis of the Physico-chemical parameters, the following were the conclusions drawn: The alkalinity ranged from 284-536mg/l. Water is very hard and unfit for any use. Heavy metals like iron and zinc were found in the lake. The coliform count was very high, more than 1000 per 100 ml of water. The chlorides were also found to be high, making the water unfit for irrigation purposes also. This result indicates sewage pollution and eutrophication of the lake. The hardness was found to be very high (160-1170 mg/l CaCO3) in the ground water in some areas.

The catchment yield was more than sufficient to fill the lake all through the year.

The people in the area are dependent on the lake for their daily supply of water.

The people opine that the lake should be converted into a recreation spot, after restoration.

Excessive input of domestic sewage and industrial effluent from the surrounding areas (particularly BEL)

The water already present was completely drained before any restoration work was implemented.

Dredging of the sediments in the lake had been carried out. The sediments so removed was transported elsewhere after de-watering to prevent them from re-entering the lake. These were used as manure.

The lake bottom was covered with some material (could be fresh mud) to prevent recontamination of the water by contact with the already existing soil.

The wastewater could also acted as a source of water to the lake after effective treatment to the water.

The weeds (like water hyacinth) were removed and fishes and native species of plants are introduced in their place.

The conveyance of run-off water into the lake was covered with grass in order to trap the sediments in the run-off.

People should be taught the importance of preserving the lake, so that dumping of wastes and carcasses is stopped.

A good vegetative cover and maintenance of a riparian area around the lake was also effective in filtering the run-off.

After months of sincere hard work, the Hebbal lake was finally complete. The dream of making a contaminated lake a paradise not only for humans but also for a wide range of birds had finally come true. Now it is all of our duty to protect this lake and work dedicatedly toward the betterment of other lakes.