Attached are articles presented at Conference Balwois which was held in Ohrid, Republic of FYROM from 25 to 29 May 2010. More about conference can be found here.

Mónika Lakatos, Tamás Szentimrey, Zita Bihari
Hungarian Meteorological Service, Hungary

The ECA indices and some other special own developed precipitation indices are realized at the Hungarian Meteorological Service. Long time daily precipitation sums series were homogenized and the climate indices series based on daily data has been analyzed for the period 1901-2008. Several extreme dry indices (maximum number of consecutive dry days, percentage of wet days (daily sum≥ 1 mm, etc.) calculation results and the fitted linear trend statistics were tested on the original and on the homogenized daily data as well. The homogenization and complementing of daily data series were performed by method MASH (Multiple Analysis of Series for Homogenization; Szentimrey). We also present the results of extreme climate indices calculations on gridded (interpolated) daily data. Gridding of homogenized daily data series was carried out by method MISH (Meteorological Interpolation based on Surface Homogenized Data Basis; Szentimrey, Bihari).
Keywords: dry day persistence, homogenization, gridding
Tamás Szentimrey, Zita Bihari
Hungarian Meteorological Service, Budapest, Hungary

The MISH (Meteorological Interpolation based on Surface Homogenized Data Basis; Szentimrey, Bihari) spatial interpolation method was developed at the Hungarian Meteorological Service. The main difference between MISH and the geostatistical interpolation methods built in GIS can be found in the amount of information used for modelling the necessary statistical parameters. In geostatistics the usable information or the sample for modelling is only the predictors, which are a single realization in time. While in meteorology we have spatiotemporal data, namely the long data series which form a sample in time and space as well. The SPI (Standardized Precipitation Index) series are often applied to characterize the drought variability within a region. The SPI values are certain transformed values of the precipitation sums assuming gamma distribution. After the transformation procedure the elements of the SPI series have expectedly standard normal distribution. However the SPI series can be calculated for station data series while there is the need to obtain gridded data series or mapping of SPI. In order to solve the above problem the following possible procedures are planned to compare during our presentation: - Gridding, interpolation of SPI series by geostatistical methods. - Calculation of SPI series based on the gridded precipitation series obtained by MISH. - Gridding, interpolation of SPI series by MISH.
Keywords: SPI, interpolation, MISH, gridding
Milena Kercheva, Zornitsa Popova
Institute of Soil Science “Nikola Poushkarov, Bulgaria

The impact of droughts on agricultural crops depends mainly on net precipitation distribution during the vegetation period and soil physical properties. Most of drought indices do not reflect the complicate interaction between current climate conditions, soil properties and crop water demands. This study compares the identification of summer drought by some wide-spread drought indices (seasonal net precipitation, SPI, PDSI and simplified water balance) with net irrigation requirements and irrigation scheduling for maize. The case study is conducted using long-term records of climate data for Sofia region and simulation of irrigation scheduling of maize grown on soils with contrastive properties: low water permeable Vertisol of high water holding capacity (180 mm m-1) and medium permeable Chromic Luvisol of 140 and 106 mm m-1 total available water. The irrigation schedule was performed using CROPWAT program (Smith, 1992). For this study the alternative with constant application depth of 60 mm that partially refills the soil reservoir was adopted. The percent of years of high irrigation demands when more than two irrigation events are required is 26%, 13% and 42%, respectively for soils with medium, high and low water holding capacity. The statistical analyses relative to the studied period indicate some deviations of the estimates given by climate indices and those of the net irrigation requirements. Taking into account the practical use of the results it is recommended to use probability of exceedance of net irrigation requirements and demands as an additional indicator for summer drought and as a basis for assessment of the other indices.
Keywords: drought indicators, irrigation scheduling, CROPWAT model, Sofia region
Zornitsa Popova and Katerina Doneva
Institute of Soil Science “Nikola Poushkarov, Bulgaria

Variability of climate and soil characteristics produces uncertainties of irrigation scheduling and demands in Bulgaria. In former studies the irrigation scheduling simulation model ISAREG was calibrated for two maize hybrids of different water stress resistance in a vertisol and a chromic cambisol soils in the Thrace plain and then used to build irrigation scheduling alternatives in agreement imposed by the irrigation methods. The objective of this study is to assess the impacts of several irrigation scheduling strategies for reduces irrigation demand upon irrigations’ number and irrigation season duration (ISD) by application of the formerly validated ISAREG model to the period 1970-2005. Aiming at improved water use under furrow irrigation the following scheduling strategies are studied in the vertisol (total available water TAW=173 mm m-1): (1) refilling the soil reservoir adopting management-allowed depletion fraction (MAD) of 0.60; (2) refilling the soil reservoir adopting MAD=0.47; (3) refilling the soil reservoir adopting MAD=0.33 and (4) partially refilling the soil reservoir adopting MAD=0.47. The following irrigation scheduling alternatives for surge furrow and sprinkler irrigation are simulated in the chromic cambisol soil (TAW=136 mm m-1): (2) refilling the soil reservoir adopting MAD = 0.60; (3) refilling the soil reservoir adopting MAD = 0.40 and (4) partially refilling soil reservoir adopting MAD=0.60. Statistical analyses of results relative to the vertisol indicate that when economically justified water saving is aimed at the number of irrigation events ranges from 1 to 3 (alternative 1) and from 2 to 4 (alternative 2) and reaches 2 - 6 (alternatives 3 and 4). Comparing with the vertisol, an additional irrigation is required in soils of moderate water holding capacity (chromic cambisol) over the high and average irrigation demand years. Thus the larger are soil water reservoir (TAW) and management-allowed depletion fraction (MAD) the shorter is the irrigation season. When water is depleted from the deeper soil layers (alternatives 2 and 4) average irrigation season starts at the beginning of July and ISD is 26 - 29 days in the vertisol and 37 - 38 days in the chromic cambisol. When MAD<0.40 (alternative 3) the irrigation season predominantly begins in June and it is longer by ten dais on the average when compared with ISD relative to alternative 2.
Keywords: Irrigation scheduling, Water saving, Irrigation season duration (ISD), ISAREG model, Climate uncertainties, Soil characteristics
Zornitsa Popova Luis S Pereira

This paper reports on using independent historic datasets relative to 8 years experiments (1984-1991) with diverse irrigation treatments of maize for further testing the irrigation scheduling simulation model ISAREG in the Thracian lowlands, Bulgaria. The experiments concern 10-13 treatments, including rainfed, deficit and full irrigation in an alluvial soil (Total Available Water TAW=118 mm m-1) at Calapica, Plovdiv region. The calibration of the model produced crop coefficients Kc and depletion fractions for no stress p relative to the crop growth stages adapted to the maize variety and the local soil and climate conditions. The calibrated parameters were obtained through searching the minimal differences between observed and simulated soil water content. The model test was performed using the data relative to the experiments in 1988. The split data method was applied: the data of the full irrigation and rainfed treatments were used for calibration, while the remaining were used for validation of the derived parameters. The resulting average absolute errors of the estimate (AEE) for the soil water content are less than 0.59%w., thus indicating appropriate model parameterisation. The accuracy of the calibrated model was tested against experimental data (1984-1990) from all irrigation and rainfed treatments by comparing the computed versus observed seasonal evapotranspiration. Results show a regression slope close to the 1:1 line and an AEE smaller than 8% of the average evapotranspiration observed. The yield response factor Ky was also derived from the observed data sets for the hybrid variety used, H708, resulting in a value of 1.495. With this purpose, a statistical test was performed to compare the model predicted versus observed relative yield decrease due to water stress. The obtained results support model use for developing water saving and environmentally oriented irrigation practices in the Plovdiv region, South Bulgaria.
Keywords: Bulgaria, evapotranspiration, model testing, soil water simulation, water-yield relation.
Jožef Roškar, Gregor Gregorič
Environmental Agency of the Republic of Slovenia, Slovenia

Numerical weather prediction (NWP) models are routinely used for weather forecast. Due to increase of available computer resources in last decade, local limited area model (LAM) configurations became operational forecasting tools in most national meteorological services. Also longer, seasonal and climatological runs of LAM were performed and their potential to improve regional details in spatial distribution of precipitation was identified. Therefore application of models for drought monitoring seems to be reasonable idea; first task is to compute model climatology for drought related variables using historical reanalyzes and to develop a tool for drought monitoring in the South East Europe based on simplified interpretation of results. In order to obtain model climatology, ECMWF’s ERA Interim analyses for the period 1989-2009 were used as initial and boundary conditions. High resolution regional analyses were computed by Non-hydrostatical Meso-scale Model (NMM), developed by NOAA/NCEP. NMM is suitable for use in a broad range of applications across scales ranging from meters to continental scale. Some results of reanalysis as well as operational runs and their possible application for drought monitoring will be presented. Keywords: weather, drought, forecasting, modeling, ECMWF, SEE
Keywords: weather, drought, forecasting, modeling, ECMWF, SEE
Gregor Gregorič
Environmental Agency of Slovenia, Slovenia

Drought monitoring is a term that usually describes combination of various indicators relevant for assessment of status of drought. Many indicators (such as Standardized Precipitation Index – SPI) are applicable globally, however most of them require regional adjustment. Almost all SEE countries have applied SPI and use it in operational practice. Since drought is not local phenomenon – it usually affects larger areas across international borders – there was clearly a need to establish cooperation and possibly standardization and common platform. That is one of main tasks of the project aiming at establishment of the Drought Management Centre for Southeastern Europe (DMCSEE). Beside standardization and common web platform, project aims at establishment of closer connection between drought indicators (based mainly on weather parameters) and drought impacts. Both aspects will together result in a drought early warning system for SE Europe.
Keywords: drought, monitoring

Related documents