**Author details**

Agroecosystems, especially those rain-feed, are experiencing more frequent and pronounced water imbalances (water stress) on the soil-plant-atmosphere route. Besides the substantial reduction in yield and quality, water stress in arable areas often additionally underpins numerous other environmental constraints such as salinisation, desertification, soil organic matter depletion, biodiversity reduction, eutrophication, etc. Thus, ensuring a stable and balanced water relationship in the soil-crop route is important for the sustainability and stability

Implementation of irrigation practice in agroecosystem is one of the most effective approaches to overcome crop water stress and ensure stable and quality food supply. It was confirmed that application of irrigation systems can substantially reduce the *water footprint* (i.e. a measure for the water volume needed for the realisation of goods and/or services), notably in horticultural and fruit crops more responsive to irrigation. Irrigated agroecosystems are overspread at nearly 20% of cultivated land areas but they generate even ~40% of global food supplies. For more than 50 years (1961–2009), irrigation was one of the widely accepted and fast-growing global strategies for overcoming water stress in agroecosystems and generator of continuous stable crop yields. In the same period, irrigated areas grew almost linearly by 120% and occupied about 300 Mha worldwide. However, due to increasing demands and continuous competition for high-quality water resources in the agricultural-industrial-domestic triangle, it is quite unrealistic to expect further expansion of agricultural irrigation on the expanse of rain-feed cropping. Adaptations to modern challenges of irrigated agroecosystem (e.g. more frequent and pronounced draughts and extreme heat strikes) aim to improve water use efficiency (WUE), and are therefore more likely. Namely, most of the modern sustainable irrigation (agricultural) management strategies are focused on using hydro-/land-resources more effectively (avoiding/reducing losses and quality deterioration) and more efficiently (maximally increasing food production) which are encompassed by the concept of WUE.

Among traditional irrigation methods and systems (which dominate at nearly 95% of irrigated area) and modern ones (distributed at nearly 5% of irrigated land) existing many significant differences in WUE along with their different operational (technological) and environmentally related characteristics. For instance, traditional surface gravity-flow irrigation systems (furrows, basins, contours, *muang fai*) in comparison to modern ones (drip irrigation, lowenergised/-pressurised sprinklers) can obtain and up to two-fold lower WUE. Consequently, there is a significant potential for improvement of WUE in irrigated agroecosystems over shifting from traditional to modern irrigation systems and/or upgrading particular sections and their elements (from the water source over conveyance system to the irrigated paddocks)

Finally, improved irrigation management (scheduling, timing, frequency, depth) was confirmed as one of the most feasible approach of achieving large increases in WUE. Current soil-water regime, detected either on real-time *in situ* approach (with precise sensors, probes) or calculated based on nearby weather recordings (to obtain reference evapotranspiration, crop coefficients, effective rainfalls), may significantly optimise irrigation timing and consequently improve WUE. Processing of such instantly collected data over modern information technologies (smartphone/PC applications) represents some of the most novel approaches in

of the whole (agro) ecosystem.

2 Irrigation in Agroecosystems

of traditional systems.

irrigation agroecosystems management.

Gabrijel Ondrasek

Address all correspondence to: gondrasek@agr.hr

Department of Soil Amelioration, Faculty of Agriculture, University of Zagreb, Zagreb, Croatia

**Chapter 2**

Provisional chapter

**Informational Entropy Approach for Rating Curve**

DOI: 10.5772/intechopen.78975

Informational Entropy Approach for Rating Curve

**Assessment in Rough and Smooth Irrigation Ditch**

The assessment of water discharge in open channel flow is one of the most crucial issues for hydraulic engineers in the fields of water resources management, river dynamics, ecohydraulics, irrigation, hydraulic structure design, etc. Recent studies state that the entropy velocity law allows expeditive methodology for discharge estimation and rating curve development due to the simple mathematical formulation and implementation. A lot of works have been developed based on the entropy velocity profile supporting measurements in lab for rating curve assessment in regular ditch flows showing a good performance. The present work deals with the use of entropy velocity profile approach in order to give a general framework of threats and opportunities related to robust operational application of such laws in the field of rating curve assessment. The analysis has been carried on a laboratory flume with regular roughness under controlled boundary conditions and different stages generating an exhaustive dashboard for the better appraisal of the approaches. Finally, entropy model may represent a robust and useful tool for the

Keywords: entropy velocity ratio, relative submergence, aspect ratio, water discharge

Water discharge assessment in open channel still represents a fundamental aspect for hydraulic engineer in several operative and technical fields like water resources management, ecological flow assessment and control, drainage and irrigation system as well as runoff and flood routing model calibration and implementation. Nevertheless, the water discharge evaluation in generic open channel is heavily affected by local fluid dynamics and geometric conditions, which well arise once flow velocity measurements and morphological boundaries are available

> © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited.

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

Assessment in Rough and Smooth Irrigation Ditch

Additional information is available at the end of the chapter

water discharge assessment in rough ditches.

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.78975

Greco Michele

Abstract

1. Introduction

Greco Michele

#### **Informational Entropy Approach for Rating Curve Assessment in Rough and Smooth Irrigation Ditch** Informational Entropy Approach for Rating Curve Assessment in Rough and Smooth Irrigation Ditch

DOI: 10.5772/intechopen.78975

#### Greco Michele Greco Michele

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.78975

#### Abstract

The assessment of water discharge in open channel flow is one of the most crucial issues for hydraulic engineers in the fields of water resources management, river dynamics, ecohydraulics, irrigation, hydraulic structure design, etc. Recent studies state that the entropy velocity law allows expeditive methodology for discharge estimation and rating curve development due to the simple mathematical formulation and implementation. A lot of works have been developed based on the entropy velocity profile supporting measurements in lab for rating curve assessment in regular ditch flows showing a good performance. The present work deals with the use of entropy velocity profile approach in order to give a general framework of threats and opportunities related to robust operational application of such laws in the field of rating curve assessment. The analysis has been carried on a laboratory flume with regular roughness under controlled boundary conditions and different stages generating an exhaustive dashboard for the better appraisal of the approaches. Finally, entropy model may represent a robust and useful tool for the water discharge assessment in rough ditches.

Keywords: entropy velocity ratio, relative submergence, aspect ratio, water discharge
