fisheries and the environmental challenges of the gorai-madhumati river system
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By M. Niamul Naser, University of Dhaka Revitalizing the Ganges Coastal Zone Conference 21-23 October 2014, Dhaka, Bangladesh http://waterandfood.org/ganges-conference/TRANSCRIPT
Conference on Revitalizing the Ganges Coastal Zone
October 21-‐23, 2014
M Niamul Naser PhD Professor of Zoology
University of Dhaka, Dhaka [email protected] Cell. 01711 707217
Fisheries and the Environmental Challenges of the Gorai-‐MadhumaM
River System
Ganges (=Padma) and Gorai River System • River Ganges (Padma)
originates from Tibet-‐India border area as Ganges river ; Passes by many important towns
• Gorai is the a tributary of river Padma at KusMa conMnued as MadhumaM, Kacha and Baleswar river.
• At the mouth of Bay of Bengal this river is known as Horinghata.
• Baleswar is the eastern border of the Sunderban.
GORAI R 89 Km
MADHUMATI R 137 Km
BALESWAR R 146 Km
Why Gorai-‐MadhumaM river system is important?
• Gorai-‐MadhumaM (GM)river system supplying freshwater to the Sunderbans Mangrove Forest
• The river system is in total 372 km long • Considering Ganges dependent area,
GORAI-‐MADHUMATI serving the SWR • GM touches 16 districts of Bangladesh in its course; covering 16,100 km2 area and about 10-‐12 million people.
• Agro-‐ecologically the GM river support 8,588 km2 of crop lands
River
Fish
Culture
Ecosys-‐tem
People
NavigaMon
Riparian wetland
PolluMon Dam/ Barrage
Water
CC ??
River systems that led to civilizaHon
Tagore and Mrinalini Devi, 1883
GEOMORPHOLOGY FINDINGS
Dredging at Gorai
Dredging at Gorai (Closer look!!)
Hardinge Bridge & Gorai Bridge
Baor along the Gorai R.
Magura bridge
Magura channel
ModhumaM R.
Kalna Ferry Ghat, Norail-‐BhaMapara
Fishing at ModhumaH River
Baleswar R. touches Sunderban RF.
Close glimpses
Gorai-‐ModhumaM River BeauMes
Water Quality of GM river system Gorai river
Shamsad et al. 2014 MadhumaM river
Present study 2011-‐12 Parameters Pre-‐monsoon Post-‐ monsoon Pre-‐monsoon Post-‐ monsoon Water Depth (m) 1-‐ 1.5 1-‐1.5 2-‐3 3-‐3.5 Temperature (°C) 32-‐ 33.5 19-‐22 31-‐ 33 18-‐ 22 pH 7.6-‐7.9 7.2-‐7.8 7.7-‐ 7.8 7.6-‐7.9 Dissolved Oxygen (mg/L)
5.8-‐7.7 6.0-‐7.6 6.6 6.9
TSS (mg/L) 0.9-‐2.5 0.9-‐3.0 1.2 2.1 EC (µS/cm) 219-‐278 208-‐264 449 334 TDS (mg/l) 140-‐178 133-‐169 -‐ -‐ Hardness (mg/L) as CaCO3
112-‐158 114-‐148 170 188
Salinity Nil Nil Nil Nil Tidal influence None None Presence Presence
Biodiversity in the catchment area Gorai river AquaHc species: 37 • Cypriniformes 10 • Perciformes 4 • TetraodonHformes 1 • Siluriformes 8 • Beloniformes 1 • Channiformes 2 • Clupeiformes 6 • Synbranchi formes 1 • Decapoda 1 • Molluska 3 • AquaHc mammals 0
MadhumaM river AquaHc species: 65 • Cypriniformes 14 • Perciformes 13 • TetraodonHformes 1 • Siluriformes 15 • Beloniformes 2 • Channiformes 3 • Clupeiformes 6 • Synbranchi formes 1 • Decapoda 3 • Molluska 4 • AquaHc mammals 2
Migratory fishes
Exclusive aquaHc animals of MadhumaH River
Gorai-‐MadhumaM dependent Districts (selected) Fish ProducMon (2010-‐2011)
DoF, 2012
0 2000 4000 6000 8000 10000 12000 14000 16000
River Beel Flood plain Pond Semi-‐closed WB
Baor Shrimp farm
KushMa Magura Narail
Annual fish Catch in Rivers (mt) (2010-‐2011)
0
50
100
150
200
250
300
350
Major Carps Other Carps Cat fishes Hilsha Prawns Other fishes
KushMa Magura Narail
FINDINGS • The obvious effect of drought is that water area in riverbed decrease in size, the death and decomposiMon of aquaMc plants and animals releases nutrients such as nitrogen and phosphorus into the remaining water resulMng in dense growths of algae
• Diurnal changes in oxygen concentraMon which ulMmately threaten all aquaMc biota, especially fish.
• Drought decreases water availability and consequently disrupt fish producMon in the river
FINDINGS • River water scarcity is chronic in Gorai river • Adverse climaMc cycles lead to detrimental environmental condiMons • Drought is characterized by a sequenMal decline in rainfall, surface runoff, soil moisture, groundwater interacMon, and discharge of the rivers • As the drought progresses, floodplain and wetland areas dry, and rivers become confined to low-‐flow channels.
OTHER THREATS TO THE RIVER OPENION
River Ecosystem at Low Water Flow
Less Oxygen Area
Less Oxygen Area
Padma River Water Flow
Afroz & Rahman 2013
Irregular water flow
Lowering Trend
How much dredging can we afford?
Fish Bana @ Magura
PERSPECTIVES Openion
PerspecMves • Change in cropping pa[ern (Using less water? + nutriHonal and financial security)
• Establishment of industry (Sunflower oil, Maize oil mills?)
• Moving towards aquaculture (freshwater oxbow lake, ponds and lake)
• Ecotourism in Gorai River • Social forestry (save environment, fuel and earn money)
TAKE HOME MESSEGES CONCLUSION
Conserving the river system Ecology of the river Structures & Processes: WQ, biodiversity, hydrology, flooding etc Social benefits Goods & Services: Fish, Water supply, NavigaHons etc Valuing River services Markets, recreaHons, non-‐monetary value-‐AstheHc Planning by prioriMzing the river needs a.FuncHonal indicators: biophysical equivalences b.Ecosystem service indicators: socioeconomics equivalence
Way forward • Establishing water quality standards for river • Monitoring water qualiMes of important river system including Gorai-‐MadhumaM river
• Maintenance of ecological water flow • Human health (eg. Arsenic) and aquaMc life protecMon measure
• Planning by prioriMzing the river needs
Thank you all