The United Nations (UN) Sustainable Development Goal (SDG) \#6 reads that by 2030 universal and equitable access to safe and affordable drinking water is achieved for all In order to achieve this goal, proper and complete monitoring, capturing all the facets of safe water access, is essential. In this thesis it is argued that the current monitoring techniques come with limitations and subsequently solutions are presented to come to a more complete picture of water access.

Monitoring safe water access happens primarily through household health surveys. These surveys are often incomplete, not covering entire nations, focus on only the primary water source and are often spatially aggregated for privacy reasons. Besides, health surveys almost never include questions on consumed water volumes while that is an important indicator for proper hygiene (WELL, 1998), and something that, at the same time, should be in balance with the natural available water resources. Next to this survey based monitoring, there is the Water Point Data Exchange (WPDx) that monitors safe access by providing a platform at which the exact location and type of water access points (such as boreholes, springs, etc.) are registered. This does give more insight into the presence and usage of a variety of sources, but also the WPDx is often incomplete: not covering entire nations.

In this thesis we present a dual methodology that gap-fills the incompleteness of the WPDx database through modeling and in parallel, researches the complex local dynamics of water access, the variety of water sources used by households and the relationships between access and water consumption by means of a household survey.

By improving a machine learning biological species modeling technique (called MaxEnt), successful predictions on the number of presences of eight different water access types across Uganda were made, also into areas that have little presence in the WPDx data. It was found that population density, precipitation, elevation, poverty and groundwater storage are important indicators for the (non)presence of water access points.

Next to modeling, a survey campaign was executed in Bushenyi-Ishaka municipality, a mid-sized town in the South West of Uganda comprising a mixture of both urban and rural areas. This was done in collaboration with Makerere University (Kampala). The survey results showed that water consumption increases with education and wealth, but also with higher number of water point presences predicted by the model. It was also found that households in Bushenyi make use of an average of two different water sources on a regular basis and often express preference for sources off premises compared to on premises (piped) for both cost and perceived quality reasons.

Lastly, modi operandi were suggested for the results to improve water access such as prioritising areas with poor(est) water access and investing in rainwater harvesting, infrastructure and education.

Groundwater use has seen a significant increase in the rapidly urbanising city of Kumasi, Ghana, due to its reliability, general good quality, and low-cost development. Conversion of vegetated to urban land along with the challenges of growing groundwater abstraction has put the groundwater system at risk. This study aims to assess how the urbanisation trends in Kumasi affect the availability of groundwater resources. Sustainability is investigated by comparing (multi-)annual groundwater withdrawals to long-term average annual replenishment. Groundwater recharge is estimated in Google Earth Engine using a water-balance approach and remote-sensing datasets to bridge the hydrological data gap. Runoff is determined using the Soil Conservation Service Curve-Number (SCS-CN) method requiring soil and land-cover maps. Land-cover maps are created for 1986, 2013, and 2020 using Sentinel-2 and Landsat 8 surface reflectance products. Evapotranspiration is derived from the MODIS evapotranspiration product and precipitation is retrieved from CHIRPS. Results indicate that groundwater recharge decreased by 80% from 1986 to 2020 (124Mm3 to 28.9Mm3) attributed to a loss of permeable land (63 percentage point decrease) and intensification of urbanisation. Domestic and non-domestic groundwater consumption in 2020 is estimated to be 28.4Mm3 and 2.7Mm3 respectively. For 2020, long-term average groundwater recharge (28.9Mm3) is less than the annual abstraction (31.1Mm3) indicating current urbanisation trends are unsustainable for future groundwater availability. Under a "business as usual" scenario, population growth presents the largest challenge for the future by causing an estimated four-fold increase in groundwater consumption by 2050. Climate change and land-cover changes under the same scenario may reduce groundwater recharge by 10% and 55% respectively. This requires the implementation of policies to properly manage the groundwater resource, such as promoting low-impact development, monitoring groundwater use, and monitoring changes in the groundwater system. This study should be seen as a preliminary investigation into the components affecting groundwater sustainability. Further research is needed to assess the exact state of the groundwater system and its response to future challenges.

https://code.earthengine.google.com/b4ebac49f28c93a633eb7bd4806f409b (groundwater recharge)
https://code.earthengine.google.com/ad1a0a88240e75e3dd727a6a350edb18 (land cover changes)