The purpose of this paper is to provide a comprehensive presentation and interpretation of the Ensemble Kalman Filter (EnKF) and its numerical implementation. The EnKF has a large user group, and numerous publications have discussed applications and theoretical aspects of it. This paper reviews the important results from these studies and also presents new ideas and alternative interpretations which further explain the success of the EnKF. In addition to providing the theoretical framework needed for using the EnKF, there is also a focus on the algorithmic formulation and optimal numerical implementation. A program listing is given for some of the key subroutines. The paper also touches upon specific issues such as the use of nonlinear measurements, in situ profiles of temperature and salinity, and data which are available with high frequency in time. An ensemble based optimal interpolation (EnOI) scheme is presented as a cost-effective approach which may serve as an alternative to the EnKF in some applications. A fairly extensive discussion is devoted to the use of time correlated model errors and the estimation of model bias.

The Ensemble Kalman Filter: Theoretical formulation and practical implementation

On behalf of Mr. Koichiro Matsuura, Director-General of UNESCO, it is my great pleasure to welcome you all to this international scientific conference. Drylands are often considered fragile ecosystems, yet they have a remarkable resilience to stress. They are home to unique and well-adapted plant and animal species that we need to conserve. Some of the world’s greatest cultures and belief systems have originated in drylands. On the other hand, desertification and land degradation in drylands often result in poverty and cause environmental refugees to abandon their homes. These problems can only be addressed in a holistic manner, based on sound scientific research and findings. Solutions to the problems of dryland degradation need to be communicated as widely as possible through education at all levels. These are many reasons why UNESCO – within its mandate of science, education, culture and communication – took the intiative to organize this conference. And we are glad that so many partners have responded to our call. UNESCO considers this conference as its main contribution to the observance of the International Year of Deserts and Desertification in 2006. We have deliberately chosen the title ‘The Future of Drylands’ as we feel it is time to redefine our priorities for science, education and governance in the drylands based on 50 years of scientific research in arid and semi-arid zones. In fact UNESCO has one of the longest traditions, within the UN system, of addressing dryland problems from an interdisciplinary, scientific point of view. In 1955, the ‘International Arid Land Meetings’ were held in Socorro, New Mexico (USA). They were organized by the American Association for the Advancement of Science (AAAS), sponsored by UNESCO and supported by the Rockefeller Foundation. One important output of the International Arid Land Meetings was a book entitled The Future of Drylands, edited by Gilbert F. White and published in

United Nations Educational, Scientific and Cultural Organization (UNESCO)

The Prediction in Ungauged Basins (PUB) initiative of the International Association of Hydrological Sciences (IAHS), launched in 2003 and concluded by the PUB Symposium 2012 held in Delft (23–25 October 2012), set out to shift the scientific culture of hydrology towards improved scientific understanding of hydrological processes, as well as associated uncertainties and the development of models with increasing realism and predictive power. This paper reviews the work that has been done under the six science themes of the PUB Decade and outlines the challenges ahead for the hydrological sciences community.Editor D. KoutsoyiannisCitation Hrachowitz, M., Savenije, H.H.G., Bloschl, G., McDonnell, J.J., Sivapalan, M., Pomeroy, J.W., Arheimer, B., Blume, T., Clark, M.P., Ehret, U., Fenicia, F., Freer, J.E., Gelfan, A., Gupta, H.V., Hughes, D.A., Hut, R.W., Montanari, A., Pande, S., Tetzlaff, D., Troch, P.A., Uhlenbrook, S., Wagener, T., Winsemius, H.C., Woods, R.A., Zehe, E., and Cudennec, C., 2013. A d...

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A decade of Predictions in Ungauged Basins (PUB)—a review

Despite significant recent advancements, global hydrological models and their input databases still show limited capabilities in supporting many spatially detailed research questions and integrated assessments, such as required in freshwater ecology or applied water resources management. In order to address these challenges, the scientific community needs to create improved large-scale datasets and more flexible data structures that enable the integration of information across and within spatial scales; develop new and advanced models that support the assessment of longitudinal and lateral hydrological connectivity; and provide an accessible modeling environment for researchers, decision makers, and practitioners. As a contribution, we here present a new modeling framework that integrates hydrographic baseline data at a global scale (enhanced HydroSHEDS layers and coupled datasets) with new modeling tools, specifically a river network routing model (HydroROUT) that is currently under development. The resulting ‘hydro-spatial fabric’ is designed to provide an avenue for advanced hydro-ecological applications at large scales in a consistent and highly versatile way. Preliminary results from case studies to assess human impacts on water quality and the effects of dams on river fragmentation and downstream flow regulation illustrate the potential of this combined data-and-modeling framework to conduct novel research in the fields of aquatic ecology, biogeochemistry, geo-statistical modeling, or pollution and health risk assessments. The global scale outcomes are at a previously unachieved spatial resolution of 500 m and can thus support local planning and decision making in many of the world's large river basins. Copyright © 2013 John Wiley & Sons, Ltd.

Global river hydrography and network routing: baseline data and new approaches to study the world's large river systems

. Current global precipitation (P) datasets do not take full advantage of the complementary nature of satellite and reanalysis data. Here, we present Multi-Source Weighted-Ensemble Precipitation (MSWEP) version 1.1, a global P dataset for the period 1979–2015 with a 3-hourly temporal and 0.25° spatial resolution, specifically designed for hydrological modeling. The design philosophy of MSWEP was to optimally merge the highest quality P data sources available as a function of timescale and location. The long-term mean of MSWEP was based on the CHPclim dataset but replaced with more accurate regional datasets where available. A correction for gauge under-catch and orographic effects was introduced by inferring catchment-average P from streamflow (Q) observations at 13 762 stations across the globe. The temporal variability of MSWEP was determined by weighted averaging of P anomalies from seven datasets; two based solely on interpolation of gauge observations (CPC Unified and GPCC), three on satellite remote sensing (CMORPH, GSMaP-MVK, and TMPA 3B42RT), and two on atmospheric model reanalysis (ERA-Interim and JRA-55). For each grid cell, the weight assigned to the gauge-based estimates was calculated from the gauge network density, while the weights assigned to the satellite- and reanalysis-based estimates were calculated from their comparative performance at the surrounding gauges. The quality of MSWEP was compared against four state-of-the-art gauge-adjusted P datasets (WFDEI-CRU, GPCP-1DD, TMPA 3B42, and CPC Unified) using independent P data from 125 FLUXNET tower stations around the globe. MSWEP obtained the highest daily correlation coefficient (R) among the five P datasets for 60.0 % of the stations and a median R of 0.67 vs. 0.44–0.59 for the other datasets. We further evaluated the performance of MSWEP using hydrological modeling for 9011 catchments ( http://www.gloh2o.org .

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MSWEP: 3-hourly 0.25° global gridded precipitation (1979–2015) by merging gauge, satellite, and reanalysis data

Foram estimadas as taxas de recarga aquifera na Bacia Hidrografica do Rio Ibicui, localizada no Estado do Rio Grande do Sul, a partir da utilizacao do metodo de separacao de escoamento de base, utilizando o filtro numerico de Eckhardt (2005) com dados de medicao de vazao disponibilizados pela Agencia Nacional de Aguas. Os resultados obtidos apontaram que as taxas de recarga variaram entre 13% e 47% com relacao a precipitacao efetiva (Mattiuzi, 2013). A partir deste resultado foi realizada uma analise mais aprofundada nas sub-bacias do Passo da Cachoeira e Azevedo Sodre, nas quais foram obtidas valores de taxa de recarga de 47% e 17%, respectivamente. Foram apontados diversos fatores que podem explicar os valores das taxas de recarga, como variacoes na precipitacao, heterogeneidade geologica e hidrogeologica, e composicoes distintas dos solos da regiao.

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Estimativa de recarga a partir da separação de escoamento de base em duas sub-bacias da bacia hidrográfica do rio ibicuí/rs

Large-scale distributed hydrologic models are becoming widely used in hydrologic applications (e.g., streamflow forecasts, climate changes impacts on the hydrologic regime, irrigation and reservoir operation). In these models, the basin is generally subdivided into square grid cells in which hydrological processes are represented, but application of these models to large basins is impractical if grid cells are used with the same resolution as the best available DEM (usually with a resolution less than 100 m). Thus large-scale models often use cells with areas of tenths or hundreds of square kilometers. This work presents a comparative analysis of COTAT+ (Paz et al. 2006) algorithm using two distinct procedures to derive lower resolution river networks from higher resolution Digital Terrain Model: i) straight upscaling and ii) two-step upscaling (from higher resolution to an intermediate resolution, and from this to the coarser resolution). The derived flow networks are evaluated using a range of performance criteria. These include proximity analysis, accuracy in catchment area, and visual comparison. The quantitative assessments provide similar performances between straight and two-step upscaling procedures. However, direct comparison of both coarse resolution river networks with the higher resolution network by visual inspection shows that the two-step upscaling procedure produced a more realistic drainage network than when using the straight upscaling procedure.

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Comparação entre dois procedimentos de upscaling de redes de drenagem

The estimate of aquifer recharge is a determining factor for the sustainable management of groundwater, since it allows the maintence of the quantity and quality of water from the aquifers. There are several methods of estimating aquifer recharge that can be employed and they vary according to the characteristic of the studied area and scales of work. In the present study the recharge rates were evaluated in the Ibicuí River Basin using Baseflow Separation and Water Table Fluctuations. Taking in consideration the scale limitation, the results of the aquifer recharge estimation by both methods converged.

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Comparação de métodos de estimativa de recarga aquífera aplicados à Bacia do rio Ibicuí/RS

Reguladores da dinâmica das comunidades planctônicas e íctica em ecossistemas límnicos subtropicais

Extensive floodplains throughout the Amazon basin support important ecosystem services and influence global water and carbon cycles. A recent change in the hydroclimatic regime of the region, with increased rainfall in the northern portions of the basin, has produced record-breaking high water levels on the Amazon River mainstem. Yet, the implications for the magnitude and duration of floodplain inundation across the basin remain unknown. Here we leverage state-of-the-art hydrological models, supported by in-situ and remote sensing observations, to show that the maximum annual inundation extent along the central Amazon increased by 26% since 1980. We further reveal increased flood duration and greater connectivity among open water areas in multiple Amazon floodplain regions. These changes in the hydrological regime of the world’s largest river system have major implications for ecology and biogeochemistry, and require rapid adaptation by vulnerable populations living along Amazonian rivers.

https://iopscience.iop.org/article/10.1088/1748-9326/acb9a7/pdf

Walter Collischonn

Papers

Estimativa de recarga a partir da separação de escoamento de base em duas sub-bacias da bacia hidrográfica do rio ibicuí/rs

Comparação entre dois procedimentos de upscaling de redes de drenagem

Comparação de métodos de estimativa de recarga aquífera aplicados à Bacia do rio Ibicuí/RS

Reguladores da dinâmica das comunidades planctônicas e íctica em ecossistemas límnicos subtropicais

Increased floodplain inundation in the Amazon since 1980