Circus Lake Demo site

Area description:

The demonstration case in Romania is located in the municipality of Bucharest, in the administrative territory of 2nd district. With an area of 138 ha, the area covers several dense urban perimeters, two large parks (Circus Park and Tei Park) and two lakes that are part of these parks.

Lake Tei is part of a system of linked lakes along the Colentina River that crosses Bucharest from north-west to east. With an area of 0.75 ha, Circului Lake is an element of green infrastructure with the main role of recreation, aligned with the natural processes of ecosystems, providing benefits for the comfort and health of the inhabitants. Due to its hydraulic connection with the shallow aquifer system, the lake replenishes the aquifer with rainwater captured from the park’s hydrographic basin.

Main issues:

Declining groundwater levels in this urban area and, consequently, the water level in Circus Lake as a consequence of several hydrological and hydraulic factors influencing the zonal water balance, namely: i) climate change evidenced by reduced precipitation; ii) drastic reduction of losses in the water distribution system; iii) temporary and permanent depletion systems (including undeclared depletions).

Solutions

• Capture rainwater from the urban environment in the Tei area and reuse it to control the water level in the lake, a reliable ecological solution to support aquifer recharge while maintaining the quality of the natural environment.
• Extension of the strategic planning exercise to the entire Tei urban area and 2nd district of Bucharest (32 km2, 345,000 inhabitants). Development of a framework for managing the volume and quality of natural water (precipitation, lakes, rivers, groundwater) in urban areas, definition of sets of parameters, methods, and thresholds for assessing the volume and quality and monitoring of natural water (precipitation, lakes, rivers, groundwater) potentially contaminated by anthropogenic water.
• Assessing the performance of green infrastructure elements in specific contexts of potentially contaminated anthropogenic waters, based on tests and water balance, and defining an optimised stormwater management concept.

Objectives:

To develop an urban water balance (well-defined and as accurate as possible) for the Tei urban area, based on alternative water resources solutions (using green infrastructure).

To inform and train the local administration of Sector 2 Bucharest and other stakeholders working in this area about distinct alternative water resources solutions applied in strategic urban planning of cities.

Figure 1. General scheme of the Circus Lake – Tei area demonstration case

Activities:

• Starting from the general large-scale urban hydrogeological model of Bucharest developed in a previous project, UTCB, with the support of data from the water operator of the Municipality of Bucharest, will develop a local model of increased accuracy for the Tei area and will analyse the potential behaviour of the urban aquifer system and the volumes required for its recharge with water. The model will include water supply network losses, interaction with the sewerage network, barrier effect produced by existing subway tunnels, and permanent and temporary drainage systems;
• For the urban area of the Tei area, hydrological modelling of rainfall runoff will be developed to quantify the volumes of water that could be captured for reuse in controlling the water level of Circului Lake as well as the hydrogeology of the urban aquifer;
• A chemical water quality framework and appropriate on-site natural treatment scheme for water reuse will be designed;
• A quantitative water management assessment framework will be developed for the test site to match optimal green infrastructure solutions;
• A stress test – on maximum values of flow rates and pollutant concentrations – of urban surface water and groundwater will be defined;
• Based on the water quality parameters, the types of plants used to improve water quality and reduce toxic substances will be determined;
• Urban planning schemes will be defined in district 2 of Bucharest, based on a correct quantitative balance of water management, including possible optimal implementation schemes of green infrastructure.

Expected impact:

• Demonstrate the efficient use of various alternative water sources, with a focus on aquifer recharge through rainwater harvesting and reuse.
• Controlling the urban groundwater level in the Tei urban area and thus the water level in the Circus Lake by applying reliable alternative water source solutions (green infrastructure).
• relieving the sewerage network of additional flows produced by heavy rainfall.
• replication of the proposed rigorous urban water balance analysis and green infrastructure implementation schemes in Bucharest as well as in other cities.

Main stakeholders involved

• City Hall of Bucharest 2nd district
• Bucharest Municipal Water Operator, Apa Nova
• Administration of Lakes, Parks and Recreation Bucharest
• National Administration “Apele Române”
• Tei Community Group (Community of residents in the neighbourhood)

Links with existing local/regional/national strategies or policies

• Romania’s National Sustainable Development Strategy Horizon 2013-2020-2030
• National Climate Change Strategy 2013-2020 (2023)
• REGULATION (EU) 2020/741 on minimum requirements for water reuse

Why is a rigorous urban water balance necessary?

• Cities are expanding massively in the underground space (Figure 2). This is important for utilities, transport, storage and other uses;
• Urban planning frequently operates in two dimensions without including a full analysis of the subsurface;
• Poor appreciation of urban subsurface conditions, and in particular the failure to consider the presence of groundwater and its dynamic control in urban infrastructure planning and design (Figure 2), is recognized as the greatest cause of construction project delays and cost overruns and subsequent deterioration of urban infrastructure.

Figure 2. Shallow (and inaccurate) hydrological analysis of the introduction of green infrastructure elements (left) compared to the real picture of the underground of cities (right).