1. Water savings from investments in infrastructure Outlook 2011, Canberra 2 March 2011 Mac Kirby, Mobin-ud-Din-Ahmad, Zahra Paydar, Akhtar Abbas and Tariq Rana

2. Key messages Others, including the Productivity Commission and various natural resource economists, have commented that infrastructure improvements are likely to be less efficient and effective than buy- backs at recovering water for the environment Here I address how much water could be saved anyway? I will mostly comment on the physical aspects with some passing comments on economics The key messages are: that there is great uncertainty about how much water can be saved........ but it is unlikely to make more than a modest contribution to what we aspire to return to the environment (or save for irrigation) Corollary: careful accounting of savings is required for investments

3. Adding up potential savings I will mostly look at infrastructure (off-farm), but will also make some passing comments about potential savings on-farm Bottom up: looking at particular case studies and extrapolating Top down: looking at the big picture across the MDB and partitioning water into used, “lost” and recoverable water First, a little bit of process... I want to have a quick look at what really is “lost” water, and what savings are

4. True losses Evaporation is a true loss (but we want evaporation from rivers!) Seepage / leakage are true losses only if they go somewhere we can’t use - eg salty groundwater Seepage / leakage to fresh groundwater or a river are available for re-use in irrigation or the environment Canal River Evaporation Seepage leakage Flow returning to river

5. True losses Evaporation is a true loss - but we want evaporation from rivers! Seepage / leakage are true losses only if they go somewhere we can’t use - eg salty groundwater Seepage / leakage to fresh groundwater or a river are available for re-use in irrigation or the environment Canal River Evaporation Seepage leakage Flow returning to river A leaky canal (CSIRO study), not far from a river - return flows unknown

6. True losses and potential savings Evaporation is a true loss - saved by: piping canals (up to 100 % saving) re-aligning irrigation system layout with shorter systems (< 100%) some small savings also achievable through operations (running systems full) (<< 100%) Seepage / leakage, if true losses, can be saved by: piping canals (up to 100 % saving) Lining canals (< 100%) re-aligning irrigation system layout with shorter systems (< 100%) some small savings also achievable through operations (running systems full) (<< 100%) Message: not all savings measures are 100 % effective Canal River Evaporation Seepage leakage Flow returning to river More expensive

7. How important are return flows? Some rough figures Message: return flows could be a significant fraction of seepage / leakage 2 nd message: we don’t really know; there are few (no?) quantitative studies 100 80 65 ? 10 ? 9 Off-farm On-farm Evaporation Seepage

8. The Pratt study in the Murrumbidgee Suggested that perhaps 300 GL annually could be saved in the Murrumbidgee  ?? 1,500 GL basin-wide But... 70 GL was from river evaporation - are we really going to save that? 130 GL was from seepage and evaporation from supply and storage systems of the MIA and CIA...... of which 42 GL was seepage from 500 km of MIA canals... but... MIL’s own figures give ~ 31GL for total 2,500 km of canals So maybe seepage estimate is too high And anyway, some is a return flow - it’s not lost 100 GL is on-farm Some necessary as a leaching fraction to prevent salt build-up in the soil Some is a return flow So... Total recoverable losses are unlikely to be more than 1/3 total (  ?? 500 GL) Economically recoverable even less

9. A top down calculation, off-farm components Southern MDB diversions from MDBA water audit reports 80 % delivery efficiency (ANCID) Metering errors based on Hydro Environmental (6.8%) and GWM (10%) Seepage and leakage as a fraction of losses based on Khan, Douglass, MIL Unaccounted flows by difference, but also from MIL Return flows estimated at 10 % of diversions across MDB (van Dijk) Real savings unclear, but unlikely to be much Diversions 8500 Field delivery 6800 Losses 1700 Meter errors ~700 Seeps leaks 300-500 Evaporation escapes unaccounted 500-700 Return flows ? Potential savings <500 Real savings ? Not Economic ? For use

10. Conclusions Key messages: there is great uncertainty about how much water can be saved........ but it is unlikely to make more than a modest contribution to what we aspire to return to the environment (or save for irrigation) Corollary: careful accounting of savings is required for investments - eg assessment of return flows Delivery efficiency improvements may be desirable on other grounds, such as a better managed system, more resilient to drought

11. http://www.csiro.au/org/HealthyCountry.html Prioritising water for irrigation and the environment project funded by CSIRO Water for a Healthy Country