Topographic data processing in modeling of river network structure and watershed delineation

The automated extraction of topographic parameters from Digital Elevation Modeis (DEMs) is considered here as an alternative to traditional manual identification of basin's boundaries and river network. The capabilities of DEMs for use in simulations of river network and basin's boundaries are investigated. Processing flow for watershed and river network delineation is elaborated based on IDRISI32 and TOPAZ programs capabilities. This paper presents the methodology of delineation of hydrographic characteristics starting from the basic available source of hypsometric data – topographic map. Critical source area and DEM's resolutions are considered as steering parameters of the quality of simulated hydrographic features. Investigations of regional value of critical source area is indicated as future research path

The impact of the groundwater outflow on the runoff of the Nida River at Pinczow

Values of mean annual baseflow rates for Nida River at Pińczów have been estimated and analysed for water years 1951-1998. The analysis has shown that the base runoff from groundwater contributes significantly to the river discharge. The long-term average of annual baseflow rate for the period 1951-1998 is estimated to be 11.3 m³/s which is about 62 % of the total annual runoff. Additionally it was proved that the zone of groundwater contributing to the river runoff does not coincide with the watershed boundaries. The boundaries of the zone within which contacts of groundwater and river take place is difficult to be strictly estimated due to heterogeneity of existing aquifers. However the analysis has shown that the river runoff depends highly on the groundwater resources that are in direct contacts with surface waters

Increase in the hydrological drought risk in different geographical regions of Poland in the 20th century

The purpose of this study was to evaluate the growing threat of hydrological droughts for the territory of Poland. Using the values of the Palmer Drought Severity Index (PDSI) tendencies in the appearance of drought months were analyzed in summer months in the 20th century. An increase in the frequency of appearance of drought months was detected in last two decades. Monthly minimum values of the PDSI show statistically significant downward tendency which indicates tendency towards over drying. Mean values of the PDSI for the period 1991-2000 was significantly lower then values in the reference period 1961-1990 for the most of the territory of Poland

Foundations of the contributing areas modeling in the basin

A review of main approaches applied in rainfall-runoff modeling is presented. Chosen hydrodynamic and conceptual models are decribed. This paper stresses recently developed variable contributing areas concept. Assumptions of TOPMODEL and its modifications are introduced. Analytical presentation of topographical characteristics, regard of surface and subsurface runoff and sufficient results reported in literature suggest that this type of model could be a direction of further study

Roczna i sezonowa struktura pola opadu w zlewni nizinnej na podstawie danych naziemnych i radarowych

Weather radar technology offers a unique means for hydrological applications characterizing precipitation patterns with high space-time resolutions. In this paper rain gauge and weather radar data are applied simultaneously to improve the knowledge of seasonal and annual amount of precipitation in a protected wetland catchment in central Poland. Analysis of precipitation patterns in years 2004-2008 has demonstrated that significant improvement in the accuracy of precipitation estimation at a catchment scale can be achieved when applying radar data. Two slightly different zones have been detected within the catchment, regarding its annual and seasonal precipitation characteristics. Analysis has proved that the west part of the catchment is recharged by relatively lower precipitation in comparison to the east part situated in the vicinity of Warsaw agglomeration. Spatial differences in precipitation recharging subsurface water resources have revealed the reduced precipitation in wetland areas which are of special environmental importance. Recommendation refers to the use of high resolution rainfall data responding to the demand for better hydrological process understanding. Described technique, apart from purely hydrologic applications, may be used to identify the subsurface recharge in the areas of high environmental concern for solving water management problems.Radarowe techniki obserwacji pola opadu stanowią unikatowy element zastosowań hydrologicznych, charakteryzując opady z wysoką rozdzielczością przestrzenno-czasową. W niniejszym artykule przedstawiono wyniki rozpoznania sezonowej i rocznej zmienności opadu w chronionej zlewni bagiennej Łasicy, położonej w środkowej Polsce. Wykorzystano zarówno dane radarowe, jak i naziemne, pochodzące z posterunków opadowych. Analiza dotyczyła lat hydrologicznych 2004-2008. Wykazano, że stosowanie danych radarowych znacznie uszczegóławia pole opadu analizowane w skali zlewni. W zlewni wyróżniono dwie strefy, odmienne pod względem rocznych i sezonowych charakterystyk opadu. Wykazano, że zachodnia część zlewni jest zasilana przez relatywnie niższe opady w porównaniu z częścią wschodnią położoną w sąsiedztwie aglomeracji warszawskiej. Stwierdzono występowanie najniższych opadów na obszarach bagiennych, uznanych za szczególnie cenne przyrodniczo. Stosowanie danych radarowych o wysokiej rozdzielczości przestrzennej odpowiada potrzebie szczegółowej identyfikacji procesów hydrologicznych w skali zlewni. Niska rozdzielczość przestrzenna danych naziemnych może prowadzić do błędnych oszacowań, a w rezultacie powodować niedokładności identyfikacji opadu jako elementu bilansu wodnego. Opisana metoda oceny pola opadu, oprócz zastosowań wyłącznie hydrologicznych, może być stosowana do identyfikacji obszarów o podwyższonym ryzyku występowania deficytów wody, co jest przydatne w gospodarowaniu wodą, szczególnie na obszarach chronionych

Variability of the Palmer drought severity index and its impact on the discharge from a lowland catchment

The purpose of this study was to evaluate the growing threat of droughts as hydrological extremes. Using the values of the Palmer Drought Severity Index available from Climatic Research Unit, University of East Anglia, Norwich in the United Kingdom, tendencies in the appearance of drought months were analysed for the period from 1901 to 2002. The research was conducted for the lowland catchment located on the Mazovian Lowland within the Kampinos National Park. An increase in frequency of appearance of drought months was detected in 1951-2002, in comparison to the frequencies calculated for the whole analyzed period 1901-2002 as well as for years 1901- 1950. Relationship between the Palmer Drought Severity Index and standardized value of mean monthly discharge was approximated by the linear regression model

Streamflow changes in mesoscale lowland catchment under future climate conditions

The objective of this study was to investigate the performance of streamflow in a lowland mesoscale catchment in Poland under current and future climate conditions. Simulations of hypothetical streamflow in the future climate were facilitated by meteorological data sets from ensemble simulations from all over Europe with the Regional Climate Model CLM. Projections of precipitation and air temperature for the 21st century under the SRES A1B scenario were used as an input to the hydrological model simulating streamflow at the daily time scale. The combination of relatively moderate increase of annual precipitation sum and mean air temperature might cause lower annual discharges. The possible decrease in stream water resources might be a signal of reduced subsurface recharge and land over drying processes

Seasonal variability of potential evapotranspiration in a lowland catchment

Evapotranspiration is the main component of hydrological water cycle at a catchment scale. However it is difficult to estimate the amount of water participating in this process. The issue of estimating the potential evapotranspiration is important from the point of view of hydrological modelling. In this paper we analyzed the potential evapotranspiration at a scale of a large lowland catchment of the Liwiec River in Poland. Data from the MODIS Global Evapotranspiration (PET-MODIS) were used in the analysis covering the period 2001-2010. Monthly and yearly estimates of the PET-MODIS at a catchment scale were compared to the values calculated by the simplified Penman-Monteith equation, according to the FAO methodology, using limited data of air temperature and wind speed. Results have shown that monthly PET-FAO calculated by the simplified Penman-Monteith equation, with limited meteorological data are underestimated with regards to PET-MOD IS. In case of large catchments it is recommended to use in hydrological models such estimates as PET-MODIS, rather than PET value