EVSC20004 Lecture Notes - Lecture 5: Nagara River, Saltwater Intrusion, Stormwater
LECTURE 5: ESTUARIES – HUMANS
Human Uses
• Transport:
o Port of Melbourne: 3,100 ship visits, one of the only ports to still be based in the mouth
of a river
• Food:
o Shrimp aquaculture - main source of protein for many cultures, has increased 300%
since early 80's to 2000's
o 3/4 of marine species harvested in US use estuaries for part of their lifestyle: swimmer
crab and Blue crab
• Water Supply:
o Need for drinking, washing, industrial processes etc.
o Sacramento-San Joaquin Delta: 738,000 acres, drinking water for 20 million people,
supports large-scale agriculture - conflicts between user groups over access
• Env flows, fresh water drinks vs agriculture etc all in conflict
• Agricultural waste discharge has decreased water quality and increased invasive
species
• Recreation:
o Fishing, boating, sailing, canoeing, swimming, bird watching etc.
o Fishing - drives economy in areas surrounding estuaries
Human Impact on Estuaries
• Habitat modification/loss
o Mangroves: 50% cleared due to intensive shrimp farming in tropics, also for urban
development
o Seagrass beds: coastal infrastructure (marines, harbours, our modifications are getting
better in terms of infrastructure and less env damage), boat moorings (chains of anchors
move with tides/winds), dredging
• Moves towards natural coastal protection - mangroves being used to protect
shorelines
• Seagrass losses: due to nutrient inputs and sediment not settling
▪ Major losses around Australia: Cockburn Sound - due to nutrients, Western
Point (70% lost intertidal seagrass) - due to turbidity, created negative
feedback loop
o Rivers:
• Nagaragawa Estuary Barrage - massive wall to stop saltwater intrusion upstream,
ensures municipal water supply, controls flooding
o Water Quality: affected by inputs of nutrients, contaminants, sediments - agricultural
waste carrying nitrogen/phosphorous
• River Mouth Management
o Surrounding development can affect natural opening/closing
o Artificial River Mouth Opening (ARMO)
• Decision whether or not to artificially open is complex one
▪ Assets potentially impacted by decision:
• Socioeconomic - roads & bridges, agricultural land, swimming, fishing,
stormwater, human health
• Environmental - fish, birds, EVC's