fg
Volume XXIII |

The climate-agriculture nexus. The water footprint of maize production (Northern Bulgaria as a case study)

Abstract: The water footprint of maize production serves as a comprehensive indicator, encompassing both direct water use for crop yields and indirect water use, including virtual water trade. This indicator provides insight into the total water required throughout the production process, making it essential for understanding water sustainability in agriculture. The main objective of this research is to expand the understanding of how climate variability affects agricultural practices, focusing on promoting sustainable water use in crop production. Specifically, the study emphasizes the assessment and analysis of both green water (rainfall) and blue water (irrigation water) used in maize cultivation in Northern Bulgaria.
The study draws upon several key data sources, including climatic information (such as air temperature, and precipitation) and agricultural and statistical data from local authorities and farmers (covering crop parameters, yields, and irrigation practices). The water footprint for maize cultivation was calculated and assessed using Cropwat software. This analysis determines the irrigation needs across different crop management strategies. The investigated period was 1961-2022, with a specific focus on the water footprints during the extremely dry and wet years. The findings highlight critical areas of water usage and scarcity. Understanding the water footprint and its connection to climate and agriculture can aid in managing water resources and addressing the environmental and economic challenges associated with water scarcity and drought.

Volume XIII |

Seasonal river flow variability of the Middle and Lower Danube and its tributaries

Abstract: The seasonality of stream flow variability indicates special feature of local cycle of precipitations, evaporation and the timing of snow melt. This study presents seasonal occurrence of maximal and minimal annual flows and spatial variability of seasonal index (Is) in the Middle and Lower Danube basin. The analysis is based on 47 time series of monthly runoff (12 for the Danube and 35 for its tributaries), which are collected from public database. The results show that the maximum annual stream flow appears during all months, but with highest frequency in April for 68% from watersheds. It varies between one and 60% (Danube – Baziaz). The monthly flow is concentrated in summer–autumn hydrological season, except for the Jalomita, Siret and Prut river basins, where it is in the winter. The highest frequency of minimum monthly runoff for the Danube and the Tisza is in October and November and for the Sava and Velika Morava – in August and September. The lowest and highest monthly discharge of the given month in the entire period were recorded in different years. Seasonal index (Is) is between 0.98 and 3.18. It is about 1.00 for the Danube and more than 2.00 for the Tisza, Ialomita, Siret and Prut watersheds. Is is stability – coefficient of variation is up to 0.30 with the exception of several river basins. Stream flow variability of the Middle and Lower Danube can provide valuable information for scientific studies and integrated management of water resources.

Volume XIII |

Extreme low flow of the Topolovets and Voinishka Rivers (Danube tributaries, Bulgaria)

Abstract: The minimal stream flow is the most sensitive characteristic of stream flow. The aim of the paper is the assessment of the duration and the frequency of low flow through threshold method on daily discharges. The daily data of the two Danube tributaries (the Topolovets and Voinishka) have been used. The results present the following: low flow typically appears in the summer and episodically in the spring and winter; the duration varies between some days to month; the spatial distribution of extreme minimum flow is discrete and depends on climatic and anthropogenic activities. The method of quantiles gives good threshold level for defining extremely low stream flow, but have to apply in keeping with concrete conditions and purposes.