On transboundary and other international aquifers:

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On transboundary and other international aquifers:

what physical transboundary

interactions may need to be controlled?

Jac van der Gun

International Groundwater Resources Assessment Centre (IGRAC)

UNESCO-IHP Meeting on Transboundary aquifers - Hydrogeology and International Law,

“Focus on the Americas”, Paris, 7-9 March 2005

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Contents Contents

P f thi t ti

• Purpose of this presentation

• Functions of an aquifer and some definitions/terms

• What types of physical transboundary interactions

• What types of physical transboundary interactions may be considered for regulation?

• Role of the aquifer setting in relation to transboundary impacts

• Concluding remarks

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Functions of an aquifer:

more than a source of water only

• Source/reservoir from which water can be tapped and supplied

Ecological and environmental functions e g :

• Ecological and environmental functions, e.g.:

– Providing flow of springs and baseflow to streams – Supporting ecosystems (wetlands)

– Supporting water-table based agriculture

– Maintaining a stable level of the land surface – Buffering surface water flows g

• Technological functions, e.g.:

– Reservoir for temporary storage of water

f f ( ff f )

– Modification of water quality (buffer in time, filter, etc.) – Reservoir for temporary storage of residual heat

– Source of geothermal energy

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Definition of an aquifer Definition of an aquifer

A if bl [ t b i ] l i l

Aquifer means a permeable [water-bearing] geological formation underlain by a less permeable layer and the water contained in the saturated zone of the formation.

(Draft convention on the law of transboundary aquifers, version of February 24, 2005)

or

Aquifer means a subsurface layer or layers of rock or other geological formations of sufficient porosity and other geological formations of sufficient porosity and permeability to allow either a significant flow of

groundwater or the abstraction of significant quantitities of groundwater

of groundwater.

(European Water Framework Directive)

or

or……..

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Simplified cross section of aquifers

Simplified cross-section of aquifers

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Some other definitions Some other definitions

• Unconfined aquifer: aquifer of which the upper limit is a free

water table (water pressure there equals atmospheric pressure) ( p q p p )

• Confined aquifer: aquifer of which the upper limit is formed by an impermeable or poorly permeable rock unit (water pressure there exceeds atmospheric pressure)

there exceeds atmospheric pressure)

• Influent stream: stream losing part of its flow to a hydraulically connected aquifer

• Effluent stream: stream receiving some flow (= base flow) from a hydraulically connected aquifer

T b d if ‘i t ti ll h d if ’

• Transboundary aquifer or ‘internationally shared aquifer’:

aquifer extending across an international boundary

• International aquifer: aquifer forming part of a complex g hydrological system (streams + aquifers) that is extending across an international boundary

• Renewable Renewable or or non renewable groundwater: groundwater body non-renewable groundwater: groundwater body

receiving or not receiving significant present-day recharge.

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We prefer exact and consistent terms and definitions, but are they like that?

Examples:

No consensus on part of the definitions

or terminology

• ‘Aquifer’

• Confined (hydrogeological vs legal)

• ‘Transboundary’ vs ‘shared’ aquifers o te o ogy

Some labels are based on relative

Transboundary vs shared aquifers

• International aquifers

• Aquifer vs aquitard/non-aquifer

• Renewable vs non renewable gr water based on relative

distinctions and other subjectivities

• Renewable vs non-renewable gr water

• Related vs non-related to surface water

• Significant recharge, high permeability, etc Qualifications

may vary in space and in time

• Influent/neutral/effluent stream stretches

• Variations in time of influent/effluent

• Transition confined/unconfined in space and in time

Classifications are

• Transition confined/unconfined in time

• Small aquifers not on global maps

• Meaning ‘semi confined’ time dependent dependent on scale

in space and/or time

• Meaning semi-confined time-dependent

• ‘Non-renewable’ refers to short-term

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Example of making definitions a little more exact by using quantitative criteria

• Non-renewable groundwater: groundwater body not receiving significant present-day recharge.

• Non-renewable groundwater: groundwater body satisfying both of the following conditions:

– the mean annual volume of present-day recharge is less than 1% of the total volume stored;

– the stored groundwater is not contributing significantly to surface

t t t t d d t t

water systems or to water-dependent ecosystems.

(After UNESCO Working Group on Non-renewable Groundwater)

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Example of the effect of scale

WHYMAP’s Groundwater Resources Map of the World (BGR, UNESCO, IAH, IAEA, CGMW)

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Main physical transboundary interactions (1) Main physical transboundary interactions (1)

Intensive

Declining groundwater

abstraction

Declining

groundwater levels

(depletion of stock)

Potential impacts:

Reduction of spring flows and of river base flows Ecosystem degradation (wetlands)

Higher pumping cost

Note: g p p g

Land subsidence Induced pollution

Induced salinization (e.g. intrusion and upconing) Considerable time lag

between cause and transboundary impact

f ( g g)

Reduced access to groundwater

Economic and/or physical exhaustion of the resource if distance is large and

aquifer is unconfined

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Main physical transboundary interactions (2) Main physical transboundary interactions (2)

Artificial

Reduction of recharge of

groundwater

Reduction of groundwater level declines

Potential impacts:

Reduction or even complete canceling of impacts of declining groundwater levels

(counteracting impacts of intensive exploitation)

( g p p )

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Main physical transboundary interactions (3) Main physical transboundary interactions (3)

Changes in land

Changes in Changes in land

use and/or land use practices

groundwater levels and/or

quality Changes in recharge

quantity or quality quality

Potential impacts on:

q y q y

Potential impacts on:

Spring flows and river base flows (quantity/quality) Ecosystems (quantity/quality)

Groundwater pumping cost p p g Land subsidence

Water quality and salinity Access to groundwater g

Economic and/or physical sustainability of the resource

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Main physical transboundary interactions (4) Main physical transboundary interactions (4)

Groundwater

L k f ff ti Groundwater

quality degradation Lack of effective

pollution control

Potential impacts on:

Water quality spring flows and river base flows Ecosystems

Quality and salinity of abstracted groundwater y y g Access to good quality groundwater

Economic and/or physical sustainability of the resource Remark:

Except for karstic systems transboundary groundwater quality impacts over large

Except for karstic systems, transboundary groundwater quality impacts over large

distances require extremely long time before showing up.

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Classification of ‘international aquifers’

Classification of international aquifers

• Transboundary aquifers

• Domestic aquifers as part of a complex

transboundary SW-GW system

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Classification of ‘international aquifers’

Classification of international aquifers

1. Transboundary aquifers

Renewable groundwater

1.1 Isolated (unrelated to surface water)

1.1.1 Non-renewable groundwater 1 1 2 Renewable groundwater

Renewable groundwater

Aquifers related to surface water

1.2 Related to surface water

1.1.2 Renewable groundwater

1.2.1 Linked to transboundary stream or lake

to surface water

1.2.2 Linked to border stream or lake 1.2.3 Linked to domestic stream or lake

2. Domestic aquifers

Addressed by Watercourse

2.1 Related to surface water

2.1.1 Linked to transboundary stream or lake

Convention 1997

2.2 Related to domestic aquifer across boundary

2.1.2 Linked to border stream or lake

2.2.1 Renewable groundwater 2.2.2 Non-renewable groundwater

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Isolated transboundary aquifers Isolated transboundary aquifers unrelated to surface water bodies

(after Y. and G. Eckstein)

( )

This aquifer may or may not be recharged This aquifer is unlikely to be recharged This aquifer may or may not be recharged

depending on climatic conditions and on properties of geological strata above groundwater table.

This aquifer is unlikely to be recharged

because a confining layer prevents

percolation of infiltrating rainwater

(unless it is a semi-confining layer)

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Transboundary aquifers hydraulically Transboundary aquifers hydraulically

connected to a border stream

Border river may constitute a hydraulic barrier between Alternatively border river may receive flow from state (after Y. and G. Eckstein)

Border river may constitute a hydraulic barrier between aquifer zone in state A and that in state B. In that case, there is a low degree of interaction between both

aquifer parts and low risk of pollution by the stream.

Alternatively, border river may receive flow from state B and produce recharge to state A, while the bulk of ground-water flow passes from state B to state A.

Pollution risk in state A from state B and from border river

river.

Conditions tend to vary in space and over time.

Intensive pumping may change the situation, both domestically and across the border!

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Transboundary aquifers hydraulically Transboundary aquifers hydraulically

connected to a border stream

Border river may be recharging either side of the Typical situation in arid zones: stream and aquifer are (after Y. and G. Eckstein)

Border river may be recharging either side of the

aquifer in full hydraulic contact. Polluted river will affect aquifer zones in both states.

Typical situation in arid zones: stream and aquifer are only “weakly connected” - stream is recharging via the unsaturated zone. In this case only unidirectional contact between surface water and groundwater.

Conditions tend to vary in space and over time.

Intensive pumping may change the situation, both domestically and across the border!

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Transboundary aquifers hydraulically Transboundary aquifers hydraulically

connected to a transborder stream

Transborder river receives baseflow from aquifer zone in state B

Transborder river is influent in state B thus contributing to recharge but may be a source

aquifer zone in state B contributing to recharge, but may be a source of pollution (both may be originating partially or entirely in state A).

Intensive pumping may change the situation, both domestically and across the border!

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Transboundary aquifer hydraulically Transboundary aquifer hydraulically

connected to a domestic stream

Domestic river is receiving baseflow from aquifer in state B. Intensive groundwater abstraction in either of the two states

Domestic rivers are recharging the transboundary aquifer in state A.

Land use changes in state A may afffect abstraction in either of the two states

may reduce baseflow.

g y

quantity and quality of recharge water.

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Domestic aquifers hydraulically Domestic aquifers hydraulically connected to an international stream

International river is recharging the

aquifer in state B. Land us in state A and state B are influencing quantity and

International river is recharging the aquifer in state B, but the domestic aquifer may be its main source of base quality of recharge to this domestic

aquifer.

flow in downstream state C (impact on

flow rate and on surface water quality)

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Domestic aquifer hydraulically connected to Domestic aquifer hydraulically connected to

another domestic aquifer across the border

Domestic aquifers across a boundary may be hydraulically connected through an aquitard

……. or they may be hydraulically

connected by a stream.

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C l di k Concluding remarks

• There is still lack of consensus on some definitions and

terminology. Improvements are possible, but some degree of subjectivity and lack of precision can not be avoided.

• Harmonization between legal and technical vocabularies is

• Harmonization between legal and technical vocabularies is required.

• Groundwater has many functions, hence there may be many

t f t b d i t W h t th ll

types of transboundary impacts. We have to ensure they are all taken into account in the draft convention.

• Looking at different settings of transboundary and other g g y international aquifers may help assess the likeliness and mechanisms of producing transboundary impacts

(prioritization and proper focus).

• Domestic aquifers unrelated to surface water, but hydraulically connected to another unrelated domestic aquifer in a

neigbouring country, still seem not to be addressed legally. g g y, g y