Hydrology

The course introduces the basic concepts of the processes underlying the different components of the hydrological cycle and provides procedures for processing hydrological information useful for design and operational problems in water engineering.

In particular, the following SDGs from the 2030 Agenda will be addressed:

• Goal 6: Protect and restore water-related ecosystems, including mountains, forests, wetlands, rivers, aquifers, and lakes (6.6); substantially increase water-use efficiency across all sectors and ensure sustainable withdrawals and supply of freshwater to address water scarcity and substantially reduce the number of people affected (6.4).

• Goal 13: Improve education, awareness-raising, and human and institutional capacity on climate change mitigation, adaptation, impact reduction, and early warning (13.3).

• Goal 11: Substantially increase the number of cities and human settlements adopting and implementing integrated policies and plans towards inclusion, resource efficiency, climate change mitigation and adaptation, disaster resilience, and develop and implement holistic disaster risk management at all levels, in line with the Sendai Framework for Disaster Risk Reduction 2015–2030 (11.b).

• Goal 15: Combat desertification, restore degraded land and soil, including land affected by desertification, drought, and floods, and strive to achieve a land degradation-neutral world (15.3).

The teaching method is lecture-based.
The course includes theoretical lessons and individual classroom exercises.
The exercises cover the probabilistic analysis of rainfall, the plotting of rainfall probability curves, the analysis of a watershed, and the evaluation of flood hydrographs.

Basic knowledge of Hydraulics.
Basic computer skills and familiarity with the use of MS Office (Excel and Word).

Attendance is highly recommended.
Students who, upon presenting the appropriate documentation (D.R. no. 1598 of 2/5/2018), have been granted recognition as working students, student athletes, students in situations of hardship, or students with disabilities, will agree with the instructor on the modalities of attendance and the execution of the exercises.

INTRODUCTION

Course presentation. Development of hydrology. Practical examples related to extreme hydrological events and an overview of the main analysis methodologies.

INTRODUCTION TO THE HYDROLOGICAL CYCLE
Components of the hydrological cycle – Precipitation – Evaporation and evapotranspiration – Surface runoff – Groundwater circulation – Hydrological balance in a region – Distribution of water resources on Earth – Average annual hydrological balance of Sicily – Anthropogenic effects on the hydrological cycle.

HYDROMETEOROLOGICAL VARIABLES AND MEASUREMENTS
Classification of hydrometeorological variables – Properties of measuring instruments – Instruments for measuring hydrometeorological variables – Rain gauges – Recording rain gauges – Errors in precipitation measurement – Remote measurements – Weather radar – Hydrometric measurements – Water level measurements – Staff gauge – Float-type water level recorder – Float-type water level chart recorder – Air-bubble water level recorder – Ultrasonic sensors – Piezoresistive cells – Instruments for velocity measurement – Horizontal-axis current meters – Vertical-axis current meters – Cableways – Velocity distribution in a cross-section – Flow rate calculation – Rating curve – Hydrograph.

HYDROLOGICAL DATA
Hydrological yearbooks – Thermometry – Characteristics of meteorological stations – Daily temperature observations – Average and extreme temperature values – Rainfall measurements – Characteristics of rain gauge stations – Annual and monthly rainfall totals – Maximum intensity rainfall – Maximum multi-day rainfall events – Short-duration, high-intensity rainfall events – Snow cover – Water Observatory of the Sicilian Region – Sicilian Agrometeorological Information Service – Other hydrological data sources.

STATISTICAL AND PROBABILISTIC ANALYSIS OF HYDROLOGICAL DATA
Role of statistics within the mathematical tools of engineering – Random variables – Population and samples – Descriptive statistical analysis – Correlation and regression analysis – Frequency analysis – Definition of probability – Probability in the case of discrete and continuous variables – Probability distribution function – Probability density function – Examples of typical distributions for hydrology – Methods for parameter estimation – Choice of probability distribution – Goodness-of-fit testing with graphical and analytical methods (e.g., probability plot, Kolmogorov test).

PRECIPITATION
Estimation of average areal rainfall – Isohyetal lines – Topohyets – Intense rainfall – Available data – Rainfall probability curves – Rainfall probability curves for durations shorter than 1 hour – Areal reduction factors for intense rainfall – Design hyetographs – Rectangular hyetograph – Triangular hyetograph – Chicago hyetograph.

CHARACTERISTICS OF DRAINAGE BASINS
Definition of watershed – Watershed delineation – Shape characteristics – Slope – Orographic characteristics – Hypsographic curve – Drainage density – Hierarchical ordering of the stream network – Horton’s laws (bifurcation law, stream length law, stream area law) – Watershed analysis using GIS software.

CALCULATION OF PEAK FLOWS
Estimation of flood discharges – Empirical methods for natural basins (Kresnik, Valentini, Pagliaro, Scimemi formulas) – Envelope curve – Semi-empirical methods for natural basins (Forti, Gherardelli-Marchetti formulas) – Probabilistic analysis of flood data.

RAINFALL-RUNOFF TRANSFORMATION MODELS
Classification of Rainfall-Runoff Models (RRM) – Hydrological and hydraulic processes in RRMs – Estimation of effective rainfall – Runoff coefficient (for natural and urban basins) – Surface water depth and surface retention – Infiltration – Horton equations – Curve Number method – Rational method – Estimation of time of concentration – Isochrone method – Linear reservoir method – Unit hydrograph (UH) and Instantaneous Unit Hydrograph (IUH) methods – Soil Conservation Service dimensionless UH method – Basics of HEC-HMS software use.

OVERVIEW OF HYDROGEOLOGICAL RISK AND CLIMATE CHANGE
Definition of risk – Hydrogeological risk and extreme hydrological events: floods, landslides, and droughts – Basic concepts related to climate change.

Assessment activities are scheduled during the course. In addition, students will be required to submit a report containing the course exercises. The final evaluation will take into account the results of the ongoing assessments, the quality of the exercise report, and a final oral interview. Alternatively, students may take a single exam consisting of an oral test covering the entire course program. In this case as well, the final evaluation will take into account the quality of the exercises.

Below is an illustrative, non-exhaustive list of topics that may be covered in the learning assessments:

• Natural and anthropogenic hydrological cycle

• Hydrological variables and measuring instruments

• Hydrological yearbooks

• Frequency analysis

• Probability distributions

• Rainfall probability curves

• Watershed and its morphometric characteristics

• GIS applications for watershed analysis

• Time of concentration

• Methods for calculating effective rainfall

• Rainfall-runoff models

• Rational method

• Flood hydrograph estimation