Still, the supply can be constrained locally and/or seasonally, and also due to poor quality. In the first domain in Figure 1.1, the LWE resources represent a biophysical system, characterised both in terms of quantity’ (for instance, surface of land, energy equivalent of in situ oil, volume of aquifer water and rainfall) and quality (for instance the fertility of land, the accessibility of water supplies, and the access to oil fields). Concern over availability of adequate volume and quality of resources emerges from their vital role as inputs for economic activities, the second domain in Figure 1.1.