The environmental aspect of transboundary aquifer management is often not obvious and straightforward. In this section it is explained how the environmental aspect is related with the notion of sustainability. One way of looking at the environmental aspect of transboundary groundwater management is by considering all possible functions that groundwater and aquifers perform. One of these functions is that it sustains eco-systems. To sustain these groundwater-dependent ecosystems, groundwater resources are partly environmentally committed. Aquifers act as a transfer function that migrate and transform interventions in one location (state) into hydrogeological and environmental consequences in another place (state).

Environment and sustainability

The environmental aspect of transboundary aquifer management is increasingly considered important and has developed in parallel with the notion of sustainability. This notion can be associated with 3 different motivations and hence one can interpret 3 different meanings.

• In the first meaning the concept of sustainability is associated with groundwater resources depletion and the possible compromising of future use. In this meaning, sustainability is much related with groundwater use efficiency as in the classic groundwater development paradigm. Within this paradigm, the motivation for sustainability is people- and profit-oriented and does not implicitly mean an environmental sustainability.
• In the second meaning, people value the natural environment and ecosystems since it provides essential ecological services for the human society. For example, the natural attenuation capacity of aquifers is a low-cost alternative for the expensive artificial contamination remediation techniques. And in this sense, ecosystems provide an indirect economic use-value. The motivation is for this type of sustainability is partly planet oriented but still profit- and people-oriented.
• The third meaning of sustainability is based on an ethical and esthetical motivation for the preservation of the natural environment. People value the non-use aspects of natural environments and ecosystems because of its pure existence. They perceive utility from it since they consider it beautiful or think they should take care for it (also for future generations). Extinct of certain species and loss of biodiversity would be perceived as a loss for humankind.

Groundwater and aquifer functions

'Wetlands' by Chesapeake Bay Program

One way of looking at the environmental aspect of groundwater management is by considering all possible functions that groundwater and aquifers perform. The obvious aquifer function is that it holds groundwater that can be consumed or used productively in human activities. In this sense, aquifers are resource pools that need to be developed and managed and the groundwater is valued in its extractive consumptive and productive form.

However, when addressing the environmental aspects of groundwater one needs to look into the more hidden, in-situ functions and values of groundwater and aquifer systems:

• Groundwater has a strong dissolving capacity and substances can be stored in dissolved shape. Also large quantities of energy can be stored in it.
• Flowing groundwater may transport and dilute these dissolved substances and energy.
• It may have a buffering capacity and diluting capacity in case of spilled toxics.
• Groundwater forms a habitat for all kinds of micro-organisms that are important in sustaining biochemical processes. Bacteria found in groundwater and in the soil matrix are found to ‘eat' various contaminants giving the aquifer a natural attenuation capacity.
• Groundwater and the aquifer material have a certain strength creating an excellent platform for building eco-systems in and on top of it.
• All these transport, storage, buffering, natural attenuation, habitat and carry capacities of groundwater and aquifer systems all are crucial in ecosystem processes.

An environment assessment in transboundary aquifer manage should ideally incorporate all these functions of aquifers and groundwater. Where are the functions located and how do we value them.

Groundwater-dependent ecosystems

'Ecosystems in Peru' by Stefan Siepman

Various types of ecosystems are directly or indirectly dependent on groundwater. River ecosystems are often dependent on a groundwater sustained base-flow guaranteeing a continuous presence and flow of water in the river. Without this continuity most fluvial flora and fauna would not survive. Also lakes and wetlands may be totally or partly groundwater-fed. Without the groundwater influx these lakes and wetlands might dry up or have very shallow water depth resulting in a change of the aquatic ecosystem. Discharging groundwater may have a specific chemical and or temperature signature that favor the development of particular terrestrial ecosystems that would not develop in other habitats.  

Environmental committed groundwater flow & the transfer function

'Qanat of Khettaras, Morocco' by Jbodane

Basically, incorporating the environmental aspect in groundwater management starts with realizing that ecosystems may be depending on groundwater and that groundwater system alteration affect the functioning of these ecosystems. When developing groundwater resources for productive use in a society one has to assess where and how much groundwater is needed to sustain the ecological functions in the area: or in other words which part of the groundwater flow is environmentally committed.

In a transboundary context it is easy to understand that large-scale interventions in the environment in one state may have large effects on the functioning of ecosystems in nearby states. For example large scale land use change from natural vegetation into agricultural areas may need huge volumes of groundwater for irrigation with a consequent groundwater table drop. Possibly, the groundwater table decline expands into the neighboring country jeopardizing ecosystems such wetlands and others. 

In a transboundary context, aquifers could be seen as a sort of transfer function. Interventions (causes) at one place are migrated and transformed in the aquifer in hydrogeological and ecological consequences in another place. Other obvious transfer functions that might work transboundary are winds (airborne emissions of toxic substances) and surface water. With respect to the dynamics of the latter 2 transfer functions, aquifers are rather slow ones.

An environment assessment ideally studies where groundwater-dependent ecosystems are located, how much of the groundwater (flow) is environmentally committed and how the aquifer transfer function relates activities and interventions in one state to ecological consequences in neighboring states.