Wk 7: Water

What are water “volumes” in the water cycle? 

Stored amounts and quality of water in different parts of the cycle (e.g., groundwater, surface water).

What are water “flows” in the water cycle? 

Movement and connectivity of water via precipitation, runoff, ET, aquifers, rivers.

Catchment water balance equation 

ΔS = (P + Is + Ig) – (Q + E + ET + D + Qg).

Main inflows in a catchment water balance 

Precipitation, surface inflows, subsurface inflows.

Main outflows in a catchment water balance 

Evaporation, evapotranspiration, streamflow, subsurface outflow, diversions.

Definition of groundwater stress 

When groundwater extraction exceeds recharge; groundwater footprint > aquifer area.

Region with highest groundwater depletion 

Ganges Basin (~20 mm/yr).

Purpose of Sustainable Diversion Limits (SDLs) 

Long‑term average limit on water use for towns, industry, and agriculture.

Purpose of Baseline Diversion Limits (BDLs) 

Estimate of water use before the Basin Plan.

What is held environmental water? 

Water recovered and allocated to achieve environmental outcomes.

Major water‑quality threats in the Murray–Darling Basin 

Algal blooms, salinity, turbidity, bushfire contamination.

Definition of blue water 

Water in rivers, lakes, reservoirs, and pumped groundwater used by humans and ecosystems.

Definition of green water 

Soil‑stored rainfall available to plants and microbes; lost via transpiration and evaporation.

Definition of grey water 

Freshwater required to dilute pollutants to meet water‑quality standards.

On‑farm water balance equation 

ΔS = P + I – ET – R – D.

What causes the green‑water yield gap? 

Runoff, percolation losses, rainfall deficiency reducing productive green‑water use.

Field capacity definition 

Soil moisture after gravitational water drains; water held in micropores.

Wilting point definition 

Soil moisture level where plants can no longer extract water (hygroscopic water remains).

Relationship between ET and wheat yield 

Yield increases linearly with seasonal ET across major environments.

Key lecture message about water management 

Right water, right place, right time; basin‑scale management; blue/green/grey water; competing demands; on‑farm monitoring.