Isotope hydrology for better management of Isotope hydrology for better management of
groundwater in the arid zone groundwater in the arid zone
A.L. Herczeg and K.M.
A.L. Herczeg and K.M. KulkarniKulkarni
Isotope Hydrology Section, IAEA Isotope Hydrology Section, IAEA
Case studies from central Australia and northern India Case studies from central Australia and northern India
The arid zone
Rainfall is low or intermittent and unreliable
The need for water research is greatest because of water scarcity and growth in world population
Recharge
Recharge
Discharge
Discharge (reduced)
Groundwater Balance Groundwater Balance
Pumping New water level Pre-development
Post-development
Pre-development
Post--development (T1)
Post--development (T2)
Impact in response to change
Impact in response to change
Australia has low Australia has low
topography and topography and
large rainfall large rainfall
deficit deficit
Recharge and Recharge and runoff are low runoff are low and intermittent and intermittent
Australias
Australias arid zone: annual rainfall arid zone: annual rainfall defecit defecit
Groundwater development
Water Allocation in Australia - GL (1996/97)
Surface Water
Groundwater Total Actual use
Tot-Act % Diff NSW 9 825 2665 12 490 10 004 2486 25 VIC 5 469 780 6249 5 788 461 7 QLD 3 202 983 4 185 4 591 -406 -9 WA 855 1138 1 993 1 796 197 10 SA 740 630 1 370 1 266 104 8
TAS 403 20 423 471 -48 -11
NT 53 73 126 179 -53 -42
ACT 76 7 83 73 10 12
TOTAL 20 623 6 296 26 919 24 071 2 848 11
Economic value of irrigation of different crops
Sustainable water management
•
Environmental, economic, social and engineering criteria for assessing development proposals.•
Irrigation efficiency gains.•
Improved and coordinated management of groundwater.•
Significant provisions for groundwater dependent ecosystems.•
Urban demand management.Isotopes in the arid zone
• Widely used since the 1950’s
• Environmental tracers have produced their most useful results in the arid zone
• Isotopes often provide unique information in
such regions – recharge rates, flow rates
Many fresh groundwaters recharged
during a wetter climate
TiTi--Tree basin, central AustraliaTree basin, central Australia
Isotopes tell us recharge is by intermittent
heavy floods
-100 -80 -60 -40 -20 0
-14 -12 -10 -8 -6 -4 -2
δ18O (‰, SMOW)
Weighted-Mean Rainfall Groundwater Samples Mean Rainfall
0-50 mm/month
>200 mm/month 150-200 mm/month
100-150 mm/month
50-100 mm/month LMWL: δ2H = 6.9 δ18O + 4.5
Groundwaters: δ2H = 4.0 δ18O - 27.3
Example – Ti-Tree basin, central Australia
Groundwater dating
Great Artesian basin
flow rates of 0.2 to 0.5 m/yr
• Groundwaters up to 250,000 years old!
Groundwater Dating Groundwater Dating
SW Great Artesian Basin SW Great Artesian Basin
Love et al. (2000)
Love et al. (2000) Water Resources ResearchWater Resources Research, vol. 36(6): 1561-1574., vol. 36(6): 1561-1574.
Northern Transec t Southern Transect
Distance (km)
36Cl x 106 (atoms/L)
0 0.5 1
0 300,000 600,000 900,000
Time (years)
36 Cl/36 Cl0
Location and topography – Haryana State Location and topography – Haryana State
Groundwater flows from wet high areas to low dry areas
Fresh: < 2000 μS/cm
Brackish: 2000 – 6000 μS/cm Saline: > 6000 μS/cm
Salinity of groundwater – Haryana state
Irrigation drainage is mobilising salty
groundwater to the surface in the interior arid zone
Stable isotopes of groundwater – Haryana stae
Isotopes tell us the fresh and saline ground- water is all from rainfall – not old
seawater
Summary
•
Groundwater extraction WILL lower water tables and reduce discharge to ecosystems•
The amount of exploitation must consider an acceptable level of impact and response times•
Isotopes are a valuable tool in providing criticalquantitative information for groundwater managers
