(2) Food security in poor countries, especially in rural areas, is closely linked to local production. Food production involves both irrigated and rainfed agriculture. It is difficult to increase crop production for a growing population without consequences for catchments and their ecosystems, aquatic as well as terrestrial. To illustrate this point, food demand globally is expected to triple by 2050, partly due to a doubling of the population and partly due to an increase in living standards. Theoretically, mean productivity per hectare could be increased by a factor of ten given adequate nutrients and water. But major aquifers, such as in northern China, the Punjab and the Ogallala under the US Great Plains, are rapidly being depleted.
(3) Ecological security derives from the protection of crucial ecological goods and services in aquatic as well as terrestrial ecosystems. Changes in both consumptive water use and in water pollution will be of relevance for the ecosystems.
The three aspects of water security are linked through the dynamics of water movement through the catchment, comprising precipitation, flows above and below ground ("blue water") and evapotranspiration ("green water"). This means that water management will involve compromise. Some uses are literally consumptive use, while others produce return flows of water then available for downstream reuse. Efforts to reach hydrosolidarity while securing both water, food and environmental security will therefore have to encompass both sequential reuse of blue water along the river system, proper attention to green/blue water interactions and as pollution loads or activities that degrade water or reduce its availability.