The present study “Literature review on impact-based guidelines for stormwater treatment” provides an overview of international guidelines, which evaluate acute impacts of combined sewer overflows (CSO) on receiving surface water bodies. The overview should serve as a basis for the assessment of measured and simulated CSO impacts on Berlin surface waters within the projects “Monitor-1” and “SAM-CSO”, which are currently carried out at the Berlin Centre of Competence for Water. In contrast to the classical approach of sewer emission thresholds, impact-based guidelines focus on possible effects of CSO in the receiving surface water. Impact-based guidelines aim at deriving locally adapted measures to minimize CSO impacts to surface waters. Thanks to this local approach, potential protection measures can be planned dependent on the state of a specific river, reservoir or lake. The following study focuses on acute CSOimpacts, which were identified as relevant for the biocenosis of the River Spree in Berlin within the KWB project ISM: (i) Increased levels of unionised ammonium (NH3) through ammonium input. (ii) Low levels of dissolved oxygen (DO) through the input of degradable organic components, which lead to DO consumption. Guidelines from Germany, Austria, Switzerland, United Kingdom, France and USA are considered along with the approach by Lammersen, which assembles a number of scientific publications. The Austrian guideline (ÖWAV-RB 19) stops at distinguishing whether further investigations are necessary. In the US “CSO control policy” further analysis is delegated mostly to local institutions. The French “Arrêté du 22 juin 2007” also asks to take into consideration the local situation of the receiving water but does not give any limit values. The remaining four approaches provide a detailed evaluation scheme for critical NH3 and DO conditions, using duration-frequency-relationships. These relationships assume that pollution events of a specific duration may only occur in defined recurrence intervals (e.g. Figure 4.1). The Swiss guideline (STORM) is not suitable for dammed lowland river systems such as the Berlin River Spree, since it focuses on fast flowing rivers with salmonid fish populations. As a result there remain three approaches, which are interesting for the Berlin situation: the UPM guideline from the UK, the BWK-M7 guideline from Germany and the Lammersen-approach, which summarizes various scientific results. Apart from the dependency of critical concentrations on event duration and recurrence frequency, influence of temperature, pH and concurrent NH3-concentrations or DO-minima are considered by UPM and the Lammersen-approach. The relationships used by the three approaches for NH3 and DO are similar (see Figures 4.1, 4.3 and 4.4). Nevertheless, their comparability is limited, as the approaches generalize various local situations and cannot be derived strictly scientifically. As a first step we therefore recommend applying the three approaches to existing data from the River Spree and count the respective numbers of critical events. Based on the results it is possible to assess to which extent each approach is applicable for the situation in Berlin. As a second step experts need to evaluate the resulting critical events to distinguish suboptimal from lethal situations. For instance, the Lammersen-approach judges both (i) a two-day period with DO < 5 mg L-1 and (ii) a 30-minutes event with DO < 1.5 mg L-1 as critical. However in the Berlin River Spree (i) occurs basically continuously throughout the summer season and is tolerated by local fish species, whereas (ii) would probably lead to a major fish kill. As a consequence the prevention of (ii) should be given first priority. Based on the experience gained from the assessment of river monitoring data, simulation results can be evaluated in a third step. All the considered guidelines propose numerical simulation of sewer and receiving surface water systems. However only simple model approaches are discussed in detail, while specialized literature is suggested for complex cases. If numerical simulations are used for the planning of concrete measures, model uncertainties must be indicated to avoid feigning accuracy of results that cannot be provided. The Swiss STORM guideline suggests using Monte-Carlo simulations to calculate probabilities of the recurrence of critical events for possible management measures. We suggest a similar approach for the Berlin situation. Thus, decision makers could weigh cost against probability of success for proposed measures.