Water resource management: HSC Earth and Environmental Science Module 8

What this dot point is asking

NESA wants you to analyse how water is managed so that human demands and the needs of ecosystems are both met, in a country that is the driest inhabited continent. You need to handle catchment management, the allocation of water between users, water quality, and the difficult balance between human and environmental demand, anchored in an Australian example such as the Murray-Darling Basin.

The answer

Water is a renewable resource, replenished by the water cycle, but it is unevenly distributed in space and time and can be degraded by overuse and pollution. In Australia, with low and variable rainfall, sustainable management is essential.

Catchment management

A catchment is the area of land from which water drains into a particular river or reservoir. What happens on the land determines the quantity and quality of the water, so catchment management treats the whole catchment as a single system. It includes protecting vegetation to reduce erosion and runoff, controlling land uses that pollute water, maintaining wetlands that filter and store water, and coordinating the many users who share a catchment. Integrated catchment management recognises that upstream actions affect downstream users and the environment.

Allocation and water trading

Where demand exceeds reliable supply, water must be allocated between users such as irrigators, industries, towns and the environment. Australia uses a system of water entitlements and annual allocations: an entitlement is a long-term right to a share of available water, and the allocation is the percentage of that share released in a given year, which falls in droughts. Water can be traded, allowing it to move to higher-value uses, although trading must be managed so that it does not harm river health or downstream communities. Allocating water to the environment, not only to human users, is a deliberate policy choice.

Water quality

Managing quantity is not enough; quality matters too. Salinity is a major Australian problem: clearing deep-rooted native vegetation raised water tables and brought salt to the surface and into rivers, damaging soils and water supplies. Nutrients from fertilisers and effluent cause algal blooms, including toxic blue-green algae that have closed long stretches of the Murray and Darling rivers. Sediment from eroding land smothers habitats. Sustainable management monitors these indicators and controls the land uses that cause them.

The Australian context

The Murray-Darling Basin is the standard Australian example. It drains about one-seventh of the continent, supports a large share of Australia's irrigated agriculture, and sustains internationally significant wetlands. Decades of over-allocation, where more water was promised to users than the rivers could sustainably provide, combined with droughts to damage the river system, kill fish and dry out wetlands. The Murray-Darling Basin Plan, introduced in 2012, sets sustainable diversion limits that cap how much water can be extracted and returns water to the environment through buybacks and efficiency measures. It is administered across several states and the Commonwealth, illustrating how shared resources require cooperative governance. The plan remains contested because it pits the economic interests of irrigation communities against the environmental need to keep the rivers flowing, which is exactly the balance this dot point asks you to analyse.

Try this

Q1. Explain what is meant by an environmental flow and why it is central to sustainable water management. [3 marks]

• Cue. Define it as water left in or returned to a river to maintain ecosystem health, and explain that without it over-extraction degrades the river.

Q2. Analyse how the Murray-Darling Basin Plan attempts to balance human and environmental water demands, and why it remains contested. [5 marks]

• Cue. Discuss sustainable diversion limits and water recovery returning flow to the environment, set against the economic cost to irrigation communities and the difficulty of multi-state governance.