Haors and Wetlands
Haors and Wetlands By the arrival of monsoon, a large part of the flood plains in Bangladesh goes under water for four to six months. This is in addition to rivers, haors, baors, and beels which remain under water round the year.
Water Bodies The low-lying vast depressions to the northeastern part of Bangladesh are called the 'haor's. These areas went low because of the tectonic Dauki fault subsidence. Once in the long past, the Bay of Bengal reached to the foothills of Meghalay. The silt carried by the Brahmaputra and the northeastern hilly rivers were filling it but the Brahmaputra has shifted its course towards the west. The haors, and those vast low-lying areas dry up in winter; but there are several beels in them, those remain as water bodies round the year. The baors are the left out beds of some main distributors of the Ganga River, namely the Bhairab, the Kaliganga, the Gorai and the Kumar. These baors had drainage links with their mother river. But many of these baors became land locked as their mother rivers died.
The lowlands called beels lie everywhere, mainly in the flood plains and deltaic regions of the big rivers. Shifting of the Ganga River left three vast stretches of depressions, one to the northwest (the Chalan beel) one to the center (the Arial Beel) and the other at the southwest (Gopalganj area). Shifting of the course of rivers and land subsidence, both created the beels. Shifting of the Brahmaputra course left depressions along both sides of the Meghna river course. These areas go under water during the monsoon and the floods. The coastal lowlands are mostly encircled by polder-embankments. The Sundarbans located at the southeast Bangladesh remain open and is the largest single unit wetlands of the country. Numerous creeks and rivers crisscross these wetlands carrying salt water from the sea, during high tide. Different variety of salt tolerant trees and shrubs grow there. Both sea and estuarine fishes are available there, and some fishes are very much indigenous to this place.
National Water Policy The haors, baors, and beels were once full of fishes, and with aquatic plants and other animals made a unique eco-system indigenous to this country. But increasing human population drained these lands for rice cultivation; embankments were put to check inundation of the crops by early floods. This has led to imbalance of the nature, by loss of fish, birds, and aquatic wildlife. This has threatened the very existence of some rare birds and aquatic species. The Bangladesh government has given due importance of haors and wetlands in its National Water Policy 1999 article 4.9. Bangladesh accepting the 1971 Ramsar Waterfowl Convention in Iran, and 1992 Rio Biodiversity Convention in Brazil has special concern, and is committed to revive the lost environmental balance. The National Water Policy in Article 4.13 mentions in details, the importance of haors, baors, and beels of this country, and states government policy on their conservation.
Seasonal Wetlands As there are major variations in rainfall from summer to spring, the wetlands in Bangladesh expand and shrink on an annual cycle. Rainfall is the minimum during winter and spring; so by March, water from the lowlands and lakes gets drained down to the lowest levels, everywhere. In April, the thunderstorms starts, so the lowlands start to get filled at places again. Rainfall for consecutive days in this period, sometimes, brings flash floods to the northeastern rivers. As the average ground level in the haor areas are very low, the flash floods fill the lowlands having no embankments. If the flood level in the river is higher, it overtops the submergible embankments, and inundates the boro crop fields of vast areas, inflicting colossal damage to the nation. Seasonal floods occur by the rise of water levels in the Ganga and the Brahmaputra, the two major rivers in Bangladesh. This happens in the seasons of monsoon and floods. Though the flood embankments protect a large portion of the country, normal water rise in those two rivers inundate lands outside the embankments, covering about 20% of the country. These seasonal wetlands, together with the permanent wetlands 10%, cover about 30% of the country are normal water bodies, in the seasons of monsoon and floods.
Major Wetlands The major wetlands lie in Sunamganj district where the Tanguar haor is the lowest pocket in Bangladesh. The other major wetlands in Sunamganj district are' Sangair, Joalbhanga, Kalnar, Khai, Dekar, Nandair, Naluar, Chaptir, Kalikota, Bharmohona, Halir, Pagnar Angurali, Karchar, Sonir, Matian, Gurmer, Kanamaiya, Pashua and Rui haors. Major wetlands in Sylhet district are Hailkar, Jilkar, Patharchauli, Jainkar, Chauldhani, Balai, Muria, Erali and Damrir haors. Major wetlands in Maulabibazar district are Hakaluki, Kawadighi, Karaiya and Hail haors. Major wetlands in Habiganj are' Guingajuri, Makar, Sonadubi and Amadir haors. In Netrokona are Ghoradoba, Singer, Dingapota, Murali and Karmohuri haors. In Kishoreganj are Humaipur, Bara Digha, Dhakir, Gopedighi, Badla, Sonabandha and Dhanpur haors. In Brahmanbaria are Medir, Pattan and Akashishapla haors. Other than haors there are major beels named Gugurajala in Chandpur, Beel Dakatia in Khulna, Mathura beel in Satkhira, Kendua beel in Bagerhat, Baghia beel in Gopalganj, Chatar beel in Perojpur, Veoa beel in Chapai Nababganj, Chalan beel in Rajshahi and Natore, Lautarar Pathar in Sirajganj, Ghugudaha beel and Gandahasti beel in Pabna, and Arial beel in Dhaka and Munshiganj districts.
Wetlands Soils The seasonal wetlands being floodplains of the rivers are covered with sandy, or silty, or silt mixed sandy soils. It has some clay soils at patches, carried and deposited by the rivers. But, the all season wetlands have thick deposit of clay mixed organic soils. This happens because of carrying finer particles and clay soils from distant sources, and accumulating in deep inland, away from the rivers. The all season wetlands also accumulate suspended organic solids, and have deposition of the fossils of aquatic plants. At certain areas, where the fossil percentage is higher, the soil is called peat. These are unconsolidated deposits of semi-carbonized plants, containing about 60% carbon, and about 30% oxygen. Two large parts of the country in Madaripur, Gopalganj, Narail, Khulna, Bagerhat and Perojpur districts and Sunamganj, Netrokona, Kishoreganj and Habiganj districts have peat soils near the ground, or just few meters below the ground. Peat soils are also found at the fringes of some other lowlands, under a layer of silt or sandy topsoil. All these happened because of morphological changes in the adjacent rivers, when they started carrying sand and silt during floods, and deposited them over the subsiding fossil soil.'
Wetlands Vegetations The vegetations of the haor areas are of such types that, they can survive inside water, or can withstand against prolonged flooding. Some of those vegetations are common in other lowlands of the country. Submerged plants are panikola, ghechu; floating plants kochuripana, kuripana; rooted floating plants shapla, paniphal, makhna; floodplain grassland binna, khag, nolkhagra; swamp forest hijol, koroch, barun etc. Bangladesh has vast coastal lowlands subject to inundation during high tides. Major parts of these lowlands are protected by embankments against tidal waters and surge. Areas not protected by embankments have mangrove forests. The Sundarbans is the largest of such forest located to the southwest.
Wetlands Birds The wetlands to the northeast are worldwide famous, for being the habitat of migratory birds. These important lowlands are, Tanguar Haor, Pashua Beel, Gurmer Haor, Hakaluki Haor, Hail Haor, Khaliajuri Area, Companiganj Area, Bara Haor, Kawadighi Haor, and Balai Haor. The Ramsar Convention on Wetlands of Importance, especially as Waterfowl Habitat was the outcome of an international meeting in 1971 at Ramsar, in Iran. This convention outlined specific criteria on water fowl count, to declare a wetland of international importance. These are, when the wetland regularly supports 20,000 waterfowl; or it regularly supports substantial numbers of individuals from particular groups of waterfowl, indicative of wetland values, productivity or diversity; or where data on populations are available, it regularly supports 1% of the individuals in a population of one species or subspecies of waterfowl. During Flood Action Plan (FAP 6), two ornithology surveys made in February-March 1992 and April-May of 1992 for the northeast haor areas. It was found that, only two sites out of them named, the Tanguar Haor and the Hakaluki Haor supported more than 20,000 waterfowls. The Tanguar Haor and the Sundarbans are declared as Ramsar sites for conservation, with international importance. The Department of Environment (DOE) has declared the Hakaluki Haor as Environmentally Critical Area (ECA) in 2000, to protect its biodiversity.
Bangladesh Birds Club does waterfowl census since 1987 at Important Bird Areas (IBA). During 2002-2004 it made census of total 61 IBA sites, the results of which is published in 2007, by the Wetlands International, Malaysia, in the book titled 'Asian Waterbird Census'. The 61 sites included 27 from Barisal, 10 from Chittagong, 7 from Dhaka, 2 from Khulna, 5 from Rajshahi and 12 from Sylhet Divisions. The Bangladesh Birds Club census counted 294,808 birds in 2002 at 33 sites, 428,674 in 2003 at 30 sites and 570,893 in 2004 at 42 sites. The census counted 105 species of water birds, 7 kingfishers and 11 raptors. It observed, major threats to the wetland birds are agricultural development, wetland reclamation, and clearance of vegetation, plantation with alien species, water bird hunting and poaching.
Wetlands Crops The Bangla calendar is a distinct crop calendar, equally divided into three cropping seasons of four months each, the Aus, the Amon and the Rabi. Traditionally, the Aus crops grow on the higher lands. The Amon crops grow on the fringes of the marshes, subject to inundation during the floods. The beds of the low-lying areas and the marshes receive organic deposits and are very rich in fertility. The varieties of rice cultivated in winter in the knee-deep water of marshlands are called the Boro rice. Draining the low-lying marshes and reclaiming lands for crop cultivation brought the possibility of cultivating Boro rice on larger areas. Therefore, different high yield varieties (HYV) rice from the Aus season were sorted out for cultivation in the late Rabi or in the early Aus periods. These cultivations are now included in the Boro rice calendar. Irrigation is provided to these crops by both groundwater lifting and surface water pumping from the adjacent channels. The problem is if starts late, the Boro rice may face flash floods at the start of summer.
Among the varieties of rice grown in the Boro season, the Hashi (BR-17), the Shahjalal (BR-18) and the Mongol (BR-19) varieties are of better quality for growing in the 'haor' areas. These varieties have shorter life; so, can be harvested before flash floods arrive at the end of spring. In recent years, HYV Boro crops of variety BR-14, BR-26, BR-29 etc., are being introduced in the haor areas, which have higher yield. But these crops have flood risks much more than others, because of their longer life. The Boro variety rice (local + HYV) has the highest average yield, 3.58 T/ha in Bangladesh, compared to Aus+Amon, 2.06 T/ha. This yield can be as much as 4.0 to 5.0 tons/ha introducing more HYV crops in Boro calendar, good water management, and input of more fertilizer per hectare (upto 300-350 kg). The present average input of fertilizer in this country is about 60 kg/ha.
Wetlands Conservation Wetlands upstream of rivers are source and reserve of water resources. These wetlands have drainage outlets, which become origin of the rivers. The origin of a river has a base flow, which can be so less that it may flow through the bed-soil of the river, and surface somewhere to the downstream. However, the wetlands' water reserves are subject to depletion by over-abstraction along their fringes, and over-drainage through their outlets. Over-abstractions of surface water resources from the reserves are done mainly for irrigation. On the other hand, over-abstraction from the groundwater around a wetland, for irrigation and water supply, accelerates deep percolation from the reserve, and fall in the water level. A large number of wetlands to the north, west, and central Bangladesh are depleted for such abstractions. Wetlands are over-drained in the name of de-silting their draining canals and rivers, by manual and mechanical dredging. Huge number of people, lots of money, and malpractices are involved in these activities. This is the root cause for drying up of the wetlands and damage to the environment. This is a chronic problem now. Over-draining mainly, to bring more and more lands under cultivation, has depleted many wetlands to the northeast, and at many other places of Bangladesh.'
Haor Embankments The flood protection methods commonly applied in the 'haor` areas are, building low height submergible embankments along the riverbanks with drainage outlets. Sudden rainfall runoff from the countryside can be drained out through these outlets. But onrush of floodwater at the advent of summer often blocks this drainage process. For this reason, farmers stand at high risk during harvest time, as their crops in the vast lowlands may get filled with 3-6 meters of rainwater, or floodwater, within a few days. As soon as the spring season departs, the normal flood flows start arriving in the rivers. The haor areas to the northeast are very low in elevation, only 2-4 meter above mean sea level in Sunamganj District. So the flood protection method applied in the haor areas (submergible embankment), appears reasonable against the onrush of flash floods. Due to low elevation, these areas can be dried only in winter, during the low flows of the rivers. Thus the haor areas are suitable for only one crop cultivation within a very limited time. [M. Inamul Haque]