The diploma thesis on "A Proposal to Optimize the Distribution Network of Water Level Gauging Stations in South Bohemian Region? deals with the distribution network of gauging stations of a category ?A?, ?B? and ?C? in the catchment area in South Bohemia. The thesis has been designed as an overview of the current situation of the gauging stations in South Bohemian Region; it is focused on the distribution network of these stations not only in the areas hit with floods. It examines whether these critical places across which the stations have been distributed since 2002 correspond to the requirements of the current flood protection, whether it would not be advisable either to increase or, on contrary, to reduce the number of stations in the exposed river areas. The data processed by Povodí Vltavy, Horní Vltava s.p. Plant, and documents by the ČHMÚ were used for the purposes of this examination. The result of the thesis is the fact that the number of the distributed gauging stations is sufficient as for the needs of flood protection, which has been found out by means of structured interviews with the respective experts. Position of these stations has been incorporated in the flood prevention plans and most of these plans have been designed just on the basis of the distribution network of the gauging stations. The critical locations have been sufficiently mapped and recorded and the flood forecasting and warning service uses the gained, very precious information from these gauging stations. The goal of the thesis was to assess the current distribution network of the gauging stations on the rivers in South Bohemian Region. The current distribution network of the gauging stations on the rivers in South Bohemian Region was studied on the basis of an analysis of the ascertained data and documents. The first goal of the examination was the issue whether the current distribution network and the number of the gauging stations correspond to the needs of protection of citizens, cultural heritage, and property, and whether it would not be advisable to increase the number of these stations. The other goal of the thesis was to optimize the gauging stations with respect to the usefulness and their distribution network, whether the distribution network corresponds to the flood protection. The current distribution network of the gauging stations was analysed by means of a partial method of field research, consulting the expert books, legal regulations and a field research. By analysing these data, I tried to find out in the thesis whether optimisation of the number and the distribution network of the water level gauging stations correspond to the current requirements of the gained data from the respective subject-matter authorities. Upon the results of the analysis of the documents, it was found out that the distribution network and optimization of all gauging stations of all categories - ?A, B, C" - meet the needs of the catchment and requirements to their distribution. Upon the gained information, it was found out that Povodí Vltavy and the operators of the gauging stations have created a very clearly organised network. The hypothesis whether the water level gauging stations are distributed on all of the important rivers in South Bohemian Region was disapproved. The gained information suggests that the gauging stations are distributed on all rivers in South Bohemian Region. The research results have revealed that there is a number of locations in danger of big flooding, however, overflowing at such areas does not put in danger people?s lives, health or property. To conclude, it can be said no matter a society is prepared for flooding as best as possible, the nature, namely water, is an element that is to be respected a lot. This is very important in terms of protection of health, life, cultural heritage and property. The thesis will be offered to the water-management authorities and administrators of the location for further use.

River discharge estimation is the basic hydrological information for most hydrological applications in various socioeconomic planning. Increasing the accuracy of the traditional rating curve in relation to river discharge estimation would be very valuable to hydrological applications. Suggestions have been made that the traditional power function rating curve should be divided into several segments because this is often motivated by the physical characteristics of the river. Each curve is commonly constructed by regression and each requires 3 estimated parameters. However stage-discharge data is often scarce, and this scarcity could lead to overparametrization and deterioration of accuracy. By constructing many unsegmented and segmented rating curves accounting for measurement uncertainty, the models can be validated, it can be determined if segmented rating curves suffers from overparametrization. The results showed that two-segmented rating curves did not yield better fits to data, and nor did it generate larger errors than unsegmented rating curves in extrapolation. Segmentation only reduced errors in low flow interpolation, when there is a clear segmentation.  It could also be concluded that unsegmented rating curves were slightly more robust when extrapolating. The biggest impact on rating curve errors was shown not to be determined by segmentation, but rather much more dependent on the amount of discharge measurement uncertainty or choice of regression method. With a mean discharge uncertainty of ±5 %, the errors from in high flow was 60 % in interpolation and 35 % in extrapolation. For low flows, the interpolation errors were around 95 % end extrapolation error estimation was 250 %. Conclusions could also be made that the relative errors from rating curves increased with lower discharges. Other important regression factors, such as heteroscedasticity, sometimes showed to have substantial impact on rating curve regressions, generally reduced from 59 % occurrence in unsegmented rating curves to 14-15 % in segmented rating curves. / Uppskattning av vattenflöden i vattendrag är den grundläggande informationen för de flesta hydrologiska applikationer vid olika typer av socioekonomisk planering. Att förbättra noggrannheten i avbördningskurvor då vattenflödet uppskattas vid en mätstation skulle vara värdefullt för de flesta tillämpningar där vattenflöden används. Tidigare studier har föreslagit att avbördningskurvor borde delas upp i flera segment, eftersom vattendrag inte sällan har olika segment med olika fysikaliska karaktärer. Varje segment kräver dock att 2-3 regressionsparametrar bestäms, men flödesmätningar vid olika vattennivåer är ofta få, och knappheten kan göra att en utökad modell blir överparametriserad och än mer osäker.   Genom att konstruera många avbördningskurvor, segmenterade och osegmenterade, kan dessa valideras mot valideringsdata och var det möjligt se om segmenterade avbördningskurvor blev överparametriserade. Studien visade att segmenterade avbördningskurvor vid kalibrering, interpolation och extrapolation generellt inte gav bättre prediktion än osegmenterade avbördningskurvor. Vid låga flöden och tydligt motiverade segmenteringar gav segmenterade avbördningskurvor en bättre interpolation, men dock inte vid extrapolation, vilket är en indikation att segmenterade avbördningskurvor var något överparametriserade. Den största inverkan på att minska felen i avbördningskurvor var var att minska mätosäkerheten i flödesmätningarna. Med en genomsnittlig mätosäkerhet i flödesmätningarna på ±5 % kunde osäkerheten kvantifieras till kring 60 % för interpolerade osegmenterade avbördningskurvor vid höga flöden och kring 95 % vid låga flöden. Variansen var dock stor. Osäkerheten från modellvalideringen av extrapolation för osegmenterade avbördningskurvor vid höga flöden kvantifierades till kring 35 % vid höga flöden och kring 250 % vid låga flöden. Resultaten visade att de relativa felen från avbördningskurvor blev större för ju lägre flödet blir.   Heteroskedastitet, som kan generera osäkerheter i avbördningskurvor, visade sig vara vanligare (59 %) i osegmenterade avbördningskurvor jämfört med segmenterade (14-15 %). Även antalet flödesmätningar hade en betydelse för felen i avbördningskurvor. / Avbördningskurva, icke-linjär regression, flöde, flödesmätning, osäkerhet, validering, hydrologi, överparametrisering, vattenstånd

Flood estimation is often required in hydrologic design and has important economic significance. For example, in Australia, the annual spending on infrastructure requiring flood estimation is of the order of $650 million ARR (I.E. Aust., 1998). Rainfall-based flood estimation techniques are most commonly adopted in practice. These require several inputs to convert design rainfalls to design floods. Of all the inputs, loss is an important one and defined as the amount of precipitation that does not appear as direct runoff. The concept of loss includes moisture intercepted by vegetation, infiltration into the soil, retention on the surface, evaporation and loss through the streambed and banks. As these loss components are dependent on topography, soils, vegetation and climate, the loss exhibits a high degree of temporal and spatial variability during the rainfall event. In design flood estimation, the simplified lumped conceptual loss models were used because of their simplicity and ability to approximate catchment runoff behaviour. In Australia, the most commonly adopted conceptual loss model is the initial losscontinuing loss model. For a specific part of the catchment, the initial loss occurs prior to the commencement of surface runoff, and can be considered to be composed of the interception loss, depression storage and infiltration that occur before the soil surface saturates. ARR (I. E. Aust., 1998) mentioned that the continuing loss is the average rate of loss throughout the remainder of the storm. At present, there is inadequate information on design losses in most parts of Australia and this is one of the greatest weaknesses in Australian flood hydrology. Currently recommended design losses are not compatible with design rainfall information in Australian Rainfall and Runoff. Also design losses for observed storms show a wide variability and it is always difficult to select an appropriate value of loss from this wide range for a particular application. Despite the wide variability of loss values, in the widely used Design Event Approach, a single value of initial and continuing losses is adopted. Because of the non-linearity in the rainfall-runoff process, this is likely to introduce a high degree of uncertainty and possible bias in the resulting flood estimates. In contrast, the Joint Probability Approach can consider probability-distributed losses in flood estimation. In ARR (I. E. Aust., 1998) it is recommended to use a constant continuing loss value in rainfall events. In this research it was observed that the continuing loss values in the rainfall events were not constant, rather than it decays with the duration of the rainfall event. The derived loss values from the 969 rainfall and streamflow events of Queensland catchments would provide better flood estimation than the recommended design loss values in ARR (I. E. Aust., 1998). In this research, both the initial and continuing losses were computed using IL-CL loss model and a single median loss value was used to estimate flood using Design Event Approach. Again both the initial and continuing losses were considered to be random variables and their probability distribution functions were determined. Hence, the research showed that the probability distributed loss values can be used for Queensland catchments in near future for better flood estimate. The research hypothesis tested was whether the new loss value for Queensland catchments provides significant improvement in design flood estimation. A total of 48 catchments, 82 pluviograph stations and 24 daily rainfall stations were selected from all over Queensland to test the research hypothesis. The research improved the recommended design loss values that will result in more precise design flood estimates. This will ultimately save millions of dollars in the construction of hydraulic infrastructures.