Downsizing parameter ensembles for simulations of rare floods

For extreme-flood estimation, simulation-based approaches represent an interesting alternative to purely statistical approaches, particularly if hydrograph shapes are required. Such simulation-based methods are adapted within continuous simulation frameworks that rely on statistical analyses of continuous streamflow time series derived from a hydrological model fed with long precipitation time series. These frameworks are, however, affected by high computational demands, particularly if floods with return periods > 1000 years are of interest or if modelling uncertainty due to different sources (meteorological input or hydrological model) is to be quantified. Here, we propose three methods for reducing the computational requirements for the hydrological simulations for extreme-flood estimation so that long streamflow time series can be analysed at a reduced computational cost. These methods rely on simulation of annual maxima and on analysing their simulated range to downsize the hydrological parameter ensemble to a small number suitable for continuous simulation frameworks. The methods are tested in a Swiss catchment with 10 000 years of synthetic streamflow data simulated thanks to a weather generator. Our results demonstrate the reliability of the proposed downsizing methods for robust simulations of rare floods with uncertainty. The methods are readily transferable to other situations where ensemble simulations are needed.

Estimation of long-term Ph changes in lakes of the Caucasus using a bioindication method based on diatomaceous analysis

To analyze processes that may lead to long-term changes in pH, lake sediments from five small lakes in the Western and Central Caucasus were studied according to diatomaceous complexes from sediment cores. A proprietary principle of hydrological parameter unification was used to reconstruct numerical pH values. In isotopic dating experiments, a series of numerical pH values for 2000–130 years were generated for the lakes. These data indicate an absence of noticeable changes in pH in the lakes of the Western Caucasus and alkalization processes in the lakes of the Central Caucasus.

Improving efficiencies of flood forecasting during lead times: an operational method and its application in the Baiyunshan Reservoir

Accurate and reliable flood forecasting plays an important role in flood control, reservoir operation, and water resources management. Conventional hydrological parameter calibration is based on an objective function without consideration for forecast performance during lead-time periods. A novel objective function, i.e., minimizing the sum of the squared errors between forecasted and observed streamflow during multiple lead times, is proposed to calibrate hydrological parameters for improved forecasting. China's Baiyunshan Reservoir basin was selected as a case study, and the Xinanjiang model was used. The proposed method provided better results for peak flows, in terms of the value and occurrence time, than the conventional method. Specifically, the qualified rate of peak flow for 4-, 5-, and 6-h lead times in the proposed method were 69.2%, 53.8%, and 38.5% in calibration, and 60%, 40%, and 20% in validation, respectively. This compares favorably with the corresponding values for the conventional method, which were 53.8%, 15.4%, and 7.7% in calibration, and 20%, 20%, and 0% in validation, respectively. Uncertainty analysis revealed that the proposed method caused less parameter uncertainty than the conventional method. Therefore, the proposed method is effective in improving the performance during multiple lead times for flood mitigation.

Study of Hydrological Parameter with Respect to DEM Using GIS & RS in Nelliampathy Hill, Kerala

Digital elevation models (DEMs) represent the total topography, surface flow is one of the more important data sources for deriving variables used by numerous hydrologic models. A lot of research has been directed to address vulnerability related with error in digital height models (DEMs) and the spread of blunder to determined terrain parameters. This audit unites a discourse of research in major topical regions identified with DEM vulnerability that influence the utilization of DEMs for hydrologic applications. The work is to give some understanding into the characterization of elevation data quality and the relationship amongst topography and water assets models. A key characteristic of circulated displaying is the spatially factor portrayal of the watershed as far as topography, vegetative, or land use/cover, soils and impenetrable territories and the subordinate model parameters that represent the hydrologic procedures of infiltration, evapotranspiration, and runoff. In our study, application of DEM and deriving hydrological parameters using remote sensing and GIS technology at Nelliampathy hill, Kerala.

KOMPOSISI DAN STRUKTUR VEGETASI DALAM POTENSINYA SEBAGAI PARAMETER HIDROLOGI DAN EROSI

The magnitude of the rain interception by the canopy is largely determined by vegetation composition and stratification. The kinetic energy of raindrops changes because the role of the vegetation part inhibits the rate of rainwater. This study aims to determine the composition and structure of vegetation in its potency as a parameter of hydrology and soil erosion. This study used a combination method between the pathway and the way the line is laid out on a sample unit which is a 200 m wide line and 20 m wide lane on each right of the river. In that path, the pots are made continuously. The results showed that vegetation composition in upstream sub region of Miu River Basin was higher than the middle and downstream areas of 19-44 species, 13-22 tribes and individual / ha 112-693 (upstream) respectively. 11-20 species, 8-13 tribes and individuals / ha 83-192 (center), 8-15 species, 6-12 tribes and individuals / ha 60-73 (downstream). The potency of vegetation as a hydrological parameter and soil erosion in Miu Sub-District is very high, which is dominated by Ficus spp. (Moraceae) with stratification of 4 levels, namely B, C, D, and E.Keywords: Composition; vegetation; watershedBesarnya intersepsi hujan oleh tajuk sangat ditentukan oleh komposisi dan stratifikasi vegetasi. Energi kinetik dari tetesan air hujan berubah karena peran bagian-bagian vegetasi yang menghambat laju air hujan. Penelitian ini bertujuan untuk mengetahui komposisi dan struktur vegetasi dalam potensinya sebagai parameter hidrologi dan erosi tanah.Penelitian ini menggunakan metode kombinasi antara cara jalur dan cara garis berpetak pada unit contoh yang berbentuk jalur sepanjang 200 m dan lebar jalur 20 m pada masing-masing kiri kanan sungai, pada jalur tersebut dibuat plot-plot berpetak secara kontinu. Hasil penelitian menunjukan komposisi jenis vegetasi pada wilayah hulu Sub DAS Miu lebih tinggi dibandingkan dengan wilayah tengah dan hilir masing-masing sebesar 19-44 jenis, 13-22 suku dan individu/ha 112-693 (hulu). 11-20 jenis, 8-13 suku dan individu/ha 83-192 (tengah). 8-15 jenis, 6-12 suku dan individu/ha 60-73 (hilir). Potensi vegetasi sebagai parameter hidrologi dan erosi tanah di Sub DAS Miu sangat tinggi yang didominasi jenis Ficus spp. (Moraceae), dengan stratifikasi 4 tingkatan yaitu B, C , D, dan E.Kata Kunci: Komposisi, vegetasi, daerah aliran sungai