Groundwater is the most abundant source of readily available (unfrozen) fresh water, making up 97 % of the global supply, with the rest found as surface and rainwater. Although it is mostly not visible, its importance is paramount in achieving positive human, environmental and economic benefits. In a humanitarian context, the preference is often to source groundwater over surface water, as surface water is generally contaminated and requires treatment prior to consumption.

For effective groundwater resource management, it is essential that resources are monitored and the appropriate data pertaining to their use, relating to both quality and quantity, are collected. The logical steps in groundwater monitoring include: (1) defining the problem; (2) drafting management objectives; (3) assessing information needs; (4) collecting data for these needs (water levels, discharge rates, water quality); (5) setting or using data storage systems (i.e. UNHCR borehole database); and (6) interpreting and disseminating the results. The development of effective management objectives is essential, and these steps can include:

1. Resource monitoring and evaluation: To understand the existing groundwater resource spatially, temporally (over time), locally (i.e. at and around the installation), and at a distance to determine if adequate safe water can be supplied based on demand;
2. Compliance monitoring: To ensure that groundwater abstraction does not adversely affect other boreholes in a well field, users of the same resource or water quality. Such compliance targets could be set and monitored by the authorities;
3. Protection monitoring: For groundwater-dependent ecosystems, other users of the aquifer, spring, and/or river must be monitored to mitigate impacts of subsidence from abstraction in urban contexts;
4. Pollution/contamination monitoring: To provide an early warning system of the potential hazards to an existing, uncontaminated resource stemming from activities such as agriculture, industry, landfills, etc.; and
5. Optimisation of pumping boreholes and/or well fields: To both meet daily demand as well as manage energy consumption.

Having well-defined monitoring objectives at the start of an intervention that are intrinsically linked to the given water indicators will ensure that strategic decisions are evidence-based. This will also help to prevent potential conflicts, such as between a refugee camp and a host community sharing the same aquifer or the negative impact on water quality from densely spaced latrines on an alluvial plain with a shallow water table and rapid infiltration rates. Monitoring resources from the beginning of the intervention will provide an alert to issues arising from sharing and public and environmental health concerns as well as greatly contribute to understanding the groundwater system in terms of aquifer types; resource availability (recharge/discharge mechanisms; aquifer properties; groundwater flow); and ultimately, response to various natural and man-made stressors (recharge and abstraction).

The data collection requirements and the frequency, scale and scope of groundwater monitoring will depend on the drafted objectives, the complexity of the context and the phase of the emergency. For example, when an affected population uses boreholes with hand pumps in the acute phase of an emergency, monitoring should at least cover the water quality parameters such as bacterial content (0 CFU/100 ml), electrical conductivity (EC or salinity), pH, temperature; the rate of abstraction (as average number of standard water buckets (5, 10 or 20 L) per family per day); and if possible, groundwater levels. Once supply is assured, more comprehensive monitoring should be included through the establishment of rainfall measurement stations and surface water measurements. The growing trend to establish a solar-powered pumping system assumes that existing boreholes are in an adequate condition to install pumps, ideally including being cased and having recently had their capacity tested. As a criterion for deciding if a borehole should be motorised as a small pumped system, the borehole safe yields should range between 5,000 and 10,000 L/hr, as compared to 1,000 L/hr for a standard hand pump. At the very least, a proper hydrogeological assessment of both the aquifer capacity (hydraulic conductivity and storage) and resource availability (recharge and discharge area) should be conducted prior to motorising boreholes. Again, this would require that the appropriate monitoring objectives are first defined and, ideally, that monitoring data is available. It is therefore recommended that boreholes be equipped with devices to monitor the groundwater level to support responsible water resource management and to avoid the over-exploitation of groundwater resources.