Spatial variability of precipitation in the area of Lodz

Abstract

This study is an attempt to determine the spatial variability of precipitation in the city of Lodz, within its administrative boundaries, and it’s a part of the larger project, which aims to develop an integrated river outflow model under a strong anthropopressure. Therefore, the hydrologic year was taken (from November 1 to October 31). To accomplish this task, the data recorded in 2010–2012 by various institutions operating within the agglomeration were used (fig. 1). Data strings from 24 rain gauges were used. However, the obtained sequences were characterized by discontinuity and the existence of various origin errors and different character. Therefore, the first task was to detect and fill the measurement gaps or to correct them. The ultimate aim of the present study was to obtain a cartographic representation of the spatial variability of precipitation in each year of the period 2010–2012 (fig. 3) and their average annual throughout this period (fig. 4), which made it possible to determine the spatial variability of water flow to the surface. Figs. 5 and 6 represent respectively the maximum daily rainfall and maximum hourly rainfall recorded in the investigated three-year period. Fig. 7 shows the average annual number of days with precipitation in the city area. Despite the very dense measurement network (which continues to be expanded) and a very high resolution of data, it was a difficult task, which required multi-step preparation and verification procedures. Data strings were incomplete or affected by errors of various kinds. One must therefore be aware of the imperfections of data collected automatically. Studies on spatial distribution of precipitation, their duration and intensity can be used to understand the causes and learn the scope of urban flooding. Creation of storm sewers control system which reacts in real-time to readings of automatic stations will avoid future losses related to sudden urban floods.