Environ Monit Assess (2019) 191: 254 https://doi.org/10.1007/s10661-019-7402-7 Combined use of the hydraulic and hydrological methods to calculate the environmental flow: Wisloka river, Poland: case study Leszek Książek & Agnieszka Woś & Jacek Florek & Maciej Wyrębek & Dariusz Młyński & Andrzej Wałęga Received: 11 November 2018 /Accepted: 18 March 2019 /Published online: 28 March 2019 # The Author(s) 2019 Abstract The scarcity of water can result in a di- hydraulic methods and determine the scientifically rect conflict between the protection of aquatic re- acceptable and cost-effective way to environmental sources and water use. For many agencies, environ- flow within a section of a mountain river with high mental flow (EF) methods are essential in environ- naturalness, on the example of the Wisłoka. In this mental impact assessments and in the protection of paper, environmental flow was calculated using important fisheries resources. The objective of this conventional hydrological methods: Tennant’s, paper is to compare selected hydrological and Tessman’s, flow duration curve and hydraulic methods, wetted perimeter method (WPM) and method based directly on ichthyofauna habitat re- : : : quirements (spawn and migration). The novelty is L. Książek A. Woś J. Florek M. Wyrębek the combined use of the hydraulic and hydrological Department of Hydraulics Engineering and Geotechnics, methods which relates to flow hydraulics based University of Agriculture in Krakow, St. Mickiewicza 24–28, 30– 059 Krakow, Poland directly on ichthyofauna habitat conditions. The hydraulic methods provide lower values of environ- mental flow in comparison with the hydrological ąż L. Ksi ek methods. The key issue in the use of the hydraulic e-mail: [email protected] methods is the choice of criteria. The development A. Woś of the required set of parameters while taking into e-mail: [email protected] account their seasonal nature shifts the method to- ward habitat modeling methods. However, the J. Florek e-mail: [email protected] scope of habitat requirements of ecosystems must be defined, including the set of aquatic organisms M. Wyrębek and watercourse type before a hydraulic method e-mail: [email protected] maybewidelyused.Beinggenerallylow-costand D. Młyński : A. Wałęga (*) simple, the methods presented in this paper can be Department of Sanitary Engineering and Water Management, applied in the water management legislative University of Agriculture in Krakow, St. Mickiewicza 24–28, 30– process. 059 Krakow, Poland e-mail: [email protected] Keywords Tessman method . Tennant method . Wetted D. Młyński perimeter method . Ichthyofauna habitat requirements . e-mail: [email protected] River morphology 254 Page 2 of 17 Environ Monit Assess (2019) 191: 254 Introduction serious limitation because it ignores the requirements of water-dependent ecosystems such as small water bodies, According to the ecosystem services concept, what man wetlands, and swamplands. They are an important part benefits from natural environment is defined as a set of of the hydrographic network and affect water circulation the products and functions of the ecosystem which is processes in a given area (Leibowitz et al. 2008; Lytle used by the community, namely provision, regulation, and Poff 2004). support, and cultural services (Costanza et al. 1997). More than 200 methods to determine environmental When applied to water resources, this relates to the flow have been developed. According to Tharme following: (i) fresh waters, generation of electric energy (2003), methods for the determination of EF can be (Operacz 2017), and inland navigation, (ii) flooded classified in four (out of six) principal groups: hydro- areas that reduce the risk of flood and also the cost of logical, hydraulic, habitat simulation, and holistic its prevention; vegetation (trees, shrubs) prevention of methods, and two secondary groups: combined and soil losses due to the effect of wind and water (Michalec other ones. Other methods are stochastic models based et al. 2017); marshes that eliminate harmful contami- on hybrid spectral and time domain approach for the nants, (iii) rivers and estuaries that provide a place for calibration of shot noise models for daily streamflow fish reproduction (Strużyński et al. 2015), transfer of generation (Morlando et al. 2016). water from the soil into plants, (iv) birdwatching, diving Hydrological methods are regarded as the simplest and snorkeling, spiritual fulfillment in rivers (Hanson and most easily used ones to calculate EF. They com- et al. 2008) and in the contact of man with water in a prise some 30% of all those used. In the hydrological wide sense. methods, the value of EF depends on the given charac- Ecological safety is also connected with the avail- teristic flow (Caissie et al. 2014). These methods are ability of water resources and the threats involved in based on monthly or daily hydrological records and are water deficiency or flood protection. As regards water recommended as suitable for EF pre-assessment in the management, a utilitarian approach is predominant, be- water management planning phase. The flow character- ing deep-rooted in human consciousness; the economic istics are relatively easy to determine if time series of aspect must not be the only criterion of water manage- daily average flows are available. In their determination, ment (Their 2016). the issues of the naturalization of flows should be con- The key points of water policy by the year 2030, sidered, i.e., the possibility of not taking into account the which is intended to prevent water deficiency and use of water, affecting the distortion of the natural drought, comprise the improvement of the retaining hydrological regime of the analyzed watercourse. The capacity of catchments, reconstruction of river continu- environmental flow should specify the requirements for ity and communication with flooded areas, development the functioning of ecosystems in relation to the natural of flood/drought prevention systems (same actions), hydrological regime. Naturalization of flows is the first water demand management forecasts in drought pe- problem that applies to hydrological methods that use riods, and water management strategies. flow characteristics. The current strong pressure on sur- A flow which satisfies water demand both in ecosys- face water and groundwater affects disruption of flows tems and water-dependent ecosystems is termed (especially low flows). The retention reservoirs, lakes, Benvironmental flow^ (EF). It is defined as the part of surface and underground water intakes, sewage dis- natural flows which should be left in a watercourse and charges (including mine water), as well as morpholog- in flooded areas in order to keep high natural values of ical transformations, i.e., maintenance and water ecosystems and water-dependent ecosystems hydrotechnical works will affect the natural hydrologi- (Tharme 2003). It is calculated as the difference between cal regime of watercourses. In connection with this, the the observed flow (Q) and what is termed instream flow question arises whether the hydrological methods for (Qn). The instream flow is defined as the amount of assessment of environmental flow could get proper flow water which should be kept in the river at its cross- in regard to habitat requirements. There is also the sectional minimum for biological and communal needs problem of the accuracy of determining low flows from (Młyńskietal.2015,ascitedinKostrzewa1980; the stage-discharge curve. Measurements of flow for Operacz et al. 2018). The parameter relates to the flow low stage can be as affected by errors. In the low-state in the riverbed only, which is deemed to be its most zone, the flow rate curve is often extrapolated due to Environ Monit Assess (2019) 191: 254 Page 3 of 17 254 lack of measurements. This is the second problem with of vertical systems. Above all, the hydraulic methods practical use of hydrological methods. How to assess are recommended for use in catchments where hydro- flows in uncontrolled catchments is the third problem. metric observations are not carried out, or for controlled Regional equations are commonly used on the world to cross sections (Efstratiadis et al. 2014)]. The wetted asses flow characteristics. On the other hand, the perimeter or maximum depth has been widely used in methods give results that can have high error. An exam- environmental flow evaluations but there is no conven- ple are results presented by Wałęga et al. (2014), where tional, objective method for selecting the critical the calculations showed significant differences between breakpoint on the curve. As described Gippel and the values of LAF (low annual flow) and MAF (mean Stewardson (1998), the point is usually chosen solely annual flow) calculated with use empirical formulas and on a subjective basis, and recommendations can vary determined on the basis of measurement data. The de- between investigators. This was the main reason carried viation of the results obtained from empirical equations out by the study that was presented in this work. was between 34 to 67% compare with observed LAF In Poland, the first attempts to determine the water and MAF. A solution in the form of regionalization volume that is required by the aquatic environment were methods was proposed in Cupak (2017) and Cupak made by Kostrzewa (1977), the author of the formula to et al. (2017). Therefore, there is a need to introduce calculate instream flow, Qn. The instream flow is a methods for calculating the environmental flow, which function of mean annual flow, MLF, and the k coeffi- will not be burdened with errors resulting from flow cient which depends on the hydrological catchment type errors. Of course, in ungauged catchments, conceptual and size: Qn = k × MLF. In Poland, calculations of envi- rainfall-runoff models can be used for determinations ronmental flow were carried out for catchment areas discharges. Chang et al. (2019) used Neuro-Fuzzy Rain- ranging from 3.62 to 28,000 km2 (Młyński et al. 2015; fall-Runoff Models for simulation of daily runoff.