This report addresses the BMBF-funded joint-project "Karst Water Technologies (KaWaTech)", which concentrates on the development and implementation of innovative water pumping and distribution concepts for subtropical and tropical (karst) regions. Among others, a pilot pumping system is realized in the province Ha Giang, Northern Vietnam, which shall secure the water supply of several thousand people in a sustainable way. As a bypass solution for hydropower plants this facility aims to utilize residual flows during the dry season through a hydropower-driven pumping system, which cannot be used-efficiently for the operation of water turbines. Beside the implementation of the machinery, comprehensive reconstruction and optimization measures have been carried out at the hydraulic infrastructure. In this context comprising investigations regarding adapted building materials have been accomplished in order to develop optimized concrete recipes based on locally available materials.The supplied water is fed into a centralized reservoir from where it is distributed to the surrounding settlements as well as to the district capital by gravity. In order to accomplish a fair water distribution a flexible distribution concept was developed which considers dynamic fluctuations of the water yield. Here, a new type of distribution tank, containing an innovative multichamber-system, enables a yield-depending but demand-oriented water supply.Furthermore, the connection of the new distribution system to the existing pipe network of the district's capital was designed. The deficient condition, which among others results from the intermittent operation, required this measure in order to avoid further damages of the infrastructure as well as to ensure the supply with sufficient network pressure.

Water scarcity can be defined as a lack of sufficient water resources or as the limited or even missing access to a safe water supply. Latter can be classified as ‘economic water scarcity’ which among others can commonly be met in tropical and subtropical karst regions of emerging and developing countries. Karst aquifers, mostly consisting of limestone and carbonate rock, show high infiltration rates which leads to a lack of above ground storage possibilities. Thus, the water will drain rapidly into the underground and evolve vast river networks. Considering the lack of appropriate infrastructure and limited human capacities in the affected areas, these underground water resources cannot be exploited adequately. Against this, background innovative and adapted technologies are required to utilize hard-to-access water resources in a sustainable way. In this context, the German–Indonesian joint R&D project “Integrated Water Resources Management (IWRM) Indonesia” dealt with the development of highly adaptable water technologies and management strategies. Under the aegis of the Karlsruhe Institute of Technology (KIT) and funded by the German Ministry of Education and Research (BMBF), these innovative technical concepts were exemplarily implemented to remedy this deficiency in the model region Gunung Sewu, a karst area situated on the southern coast of Java Island, Indonesia. The experiences gained through the interdisciplinary joint R&D activities clearly showed that even in the case of availability of appropriate technologies, a comprising transfer of knowhow and the buildup of capabilities (Capacity Development) is inevitable to sustainably implement and disseminate new methods. In this context, an adapted water supply facility was developed by KIT which hereafter shall serve for demonstration, teaching, and research purposes. The plant’s functionality, its teaching and research concept, as well as the design process, which was accomplished in collaboration with the University Gadjah Mada (UGM), Yogyakarta, Indonesia, is the content of this present paper.

Populated karst landscapes can be found all over the world, although their natural boundary conditions mostly lead to distinct challenges regarding a sustainable water supply. Especially in developing and emerging countries, this situation aggravates since appropriate technologies and water management concepts are rarely available. Against this background, the interdisciplinary, German-Indonesian joint project "Integrated Water Resources Management (IWRM) Indonesia'', funded by the German Federal Ministry of Education and Research (BMBF), focused on the development and exemplary implementation of adapted techniques to remedy the partly severe water scarcity in the region Gunung Sewu. This karst area, widely known as "Java's poorhouse'', is located on the southern coast of Java Island and distinctly suffers from the mentioned constraints. Under the aegis of the Karlsruhe Institute of Technology (KIT), the conceptual and technical achievements of the "IWRM Indonesia'' joint research project are characterized by a high potential for multiplication not only for karst areas but also for non-karst regions. One of the project's major accomplishments is the erection of an innovative hydropower-driven water supply facility located in a karst cave 100 m below ground and continuously supplying tens of thousands of people with fresh water. Referring to the plant's innovative character and the demanding conditions on-site, the implementation was a highly iterative process leading to today's autonomous operation by an Indonesian public authority. Based on the experiences gained during design, construction, operation and monitoring phase, this paper introduces an implementation approach for adapted technologies as well as a comprising technical and economical assessment of the plant's operation.