Urban agriculture lies at the core of the Water Energy Food nexus and seems to provide a partial answer to confront modern trends such as population growth, climate change and resource depletion by increasing food security in cities and enhancing sustainability in an urban realm. The assembly of a WEF nexus framework taught, however, that most work that has been published on the nexus is very hypothetical and that the acquisition of quantitative data poses the biggest challenge in WEF nexus research. The mere absence of data collected at a local level impedes informed decision making on nexus sector integration and feasibility of sustainable solutions. This study attempts to bridge the existing knowledge gap and aimed to contribute to the quantification of the nexus regarding urban agriculture. It investigates the water, energy and nutrient demand of urban farms along with the presence of those resources in urban waters at three case study sites. Demands for water and nutrients (nitrogen & phosphorus) at a greenhouse in Amsterdam and a community farm and a container farm in East-Boston could be met by resources present in urban waters (rainwater and wastewater) in the direct vicinity. Whether enough energy is available to run each of these farms is related to the type of agriculture which is applied.

Kathmandu is a prime example of a city exhibiting both rapid metropolitan region expansion and a population boom. This growth leads to a water stress and pollution of the surface and groundwater. The lack of proper waste management and sanitation results in the ongoing deterioration of the water quality in the Kathmandu Valley. The situation is worsened by the lack of a complete and safe drinking water network leading citizens to pivot on conventional water sources like stone spouts and bore wells. Consequently, groundwater extraction, from the aquifer under the Kathmandu Valley, is expected to keep increasing and the groundwater table to drop as the recharge is less than the extraction rate. This research aims to address the influences of land-use on the quantity and quality of water sources in the Kathmandu Valley and how the necessary data can be collected by citizen science in the future. The fieldwork took place in August 2017 when groundwater level, water quality and land-use data were collected from seven watersheds within the Kathmandu Valley in Nepal. At the same time, existing citizen science precipitation data were processed and juxtaposed with respective satellite data, namely IMERG GPM. On the one hand, the results confirm our initial assumption that the quality of the river water dramatically deteriorates (except for nitrite, nitrate and phosphate) while flowing through the agricultural and urban areas. Another observation is that spout water quality (except E. coli, turbidity and iron) is also negatively influenced by human activities. On the other hand, there is no clear link between land-use and wells’ water quality. A strange finding is that spouts and wells water quality do not behave similarly showcasing that they do not originate from the same aquifer. A health risk analysis was conducted with the results indicating that some water quality parameters have values exceeding the WHO standards. Regarding the option of implementing satellite data to facilitate citizen science, the contingency analysis shows that satellite products can detect the general temporal precipitation pattern although they perform poorly when it comes to estimating the correct amounts of rainfall. An extended network of rain gauges within the Kathmandu Valley is vital to establish a strong linear relationship between ground and satellite data which is, in turn, essential to enable GPM to enhance the temporal resolution of the citizen science measurements. Furthermore, the implementation of land-use and water quality measurements into citizen science shows increasing potential especially when taking into account the contribution of ODK. The accuracy of the citizen science ground truthing was found to be 33% when compared to the experts. Proper training of the citizen scientists is essential to improve performance. During research temperature, EC and turbidity were labelled as indication parameters. Those parameters are used to indicate the range of other water quality parameters which cannot be measured easily. The indication parameters, however, can be measured with affordable equipment and together with water quality strips prove to be powerful tools in the hands of citizen science. Finally, the groundwater recharge for the monsoon period was determined, but it is expected to be drastically reduced the rest of the year. A solid conclusion about the relation between recharge and land-use can’t be made unless a more substantial number of wells is regularly sampled.