Managing water
The planet is drowning in water — and has almost none to drink. Nearly all of it is salt, and most of the fresh part is frozen or buried, leaving a thin, shared ration for everything that lives. This powerbook follows that ration: how we clean and reuse water, how we drain and foul it, and how a finite resource can be shared between people and ecosystems.
The interactive book above is the lesson. What follows is a plain recap you can revise from, plus the sources and how this maps to the syllabus.
How little water is usable
About 97% of the Earth’s water is salt; only around 3% is fresh, and most of that is frozen in ice or held deep as groundwater. The fresh water readily available in lakes, rivers and soil is under one percent of fresh water — a thin ration shared by all living things.
Treating and reusing the three streams
Sewage: primary (settle solids) → secondary (microbes break down organics) → tertiary (disinfect, remove nutrients), then reuse or discharge. Industrial wastewater: treatment matched to its specific chemicals or metals. Stormwater: captured and filtered (traps, wetlands), then reused. Water is cleaned fit for purpose — to the standard its next use needs.
Direct vs indirect human impacts
Direct (availability): over-extraction — taking water faster than it refills, draining rivers (e.g. the Murray–Darling) and lowering water tables, with salt intrusion in coastal aquifers. Indirect (quality): nutrient runoff causes eutrophication and algal blooms — we add nutrients, not algae, and the bloom blocks light, releases toxins and strips oxygen as it decays, killing fish.
For HSC students
This powerbook covers the Water Management thread of Module 4 (Human Impacts), framed by the inquiry question how can water be managed for use by humans and ecosystems? Working through it, you should be able to:
- represent the distribution of the Earth’s water and the small share available to plants and animals;
- investigate the treatment and reuse of industrial wastewater, sewage and stormwater;
- describe how human activity influences water availability and quality, directly (over-extraction) and indirectly (algal blooms);
- relate these to managing a finite resource shared between people and ecosystems.
The next chapter turns to land and soil, including how clearing and irrigation cause salinity. Explanations here are original and are a study aid, not a copy of the syllabus.
Sources
- US Geological Survey — distribution of the Earth’s water (oceans, ice, groundwater, surface fresh water).
- Australian Government / state water authorities — wastewater treatment stages and recycled-water reuse (sewage, industrial, stormwater).
- Murray–Darling Basin Authority — over-extraction, environmental flows, and algal blooms in the basin.
- NSW NESA Earth and Environmental Science Stage 6 Syllabus (2017) — used only to scope the Module 4 content; explanations above are original.
The blue planet runs on a few drops. Manage water well and the cup keeps refilling; drain it and foul it, and there is no second tank to open.