Abstract. Alqueva Reservoir is one of the largest artificial lakes in Europe and is a strategic water storage for public supply, irrigation, and energy generation. The reservoir is integrated within the Multipurpose Alqueva Project (MAP), which includes almost 70 reservoirs in a water-scarce region of Portugal. The MAP contributes to sustainability in southern Portugal and has an important impact on the entire country. Evaporation is the key component of water loss from the reservoirs included in the MAP. Evaporation from Alqueva Reservoir has been estimated by indirect methods or pan evaporation measurements; however, specific experimental parameters such as the pan coefficient were never evaluated. Eddy covariance measurements were performed at Alqueva Reservoir from June to September in 2014 as this time of the year provides the most representative evaporation volume losses in a Mediterranean climate. This period is also the most important period for irrigated agriculture and is, therefore, the most problematic period of the year in terms of managing the reservoir. The direct pan evaporation approach was first tested, and the results were compared to the eddy covariance evaporation measurements. The total eddy covariance (EC) evaporation measured from June to September 2014 was 450.1 mm. The mean daily EC evaporation in June, July, August, and September was 3.7, 4.0, 4.5, and 2.5 mm d−1, respectively. A pan coefficient, Kpan, multivariable function was established on a daily scale using the identified governing factors: air temperature, relative humidity, wind speed, and incoming solar radiation. The correlation between the modelled evaporation and the measured EC evaporation had an R2 value of 0.7. The estimated Kpan values were 0.59, 0.57, 0.57, and 0.64 in June, July, August, and September, respectively. Consequently, the daily mean reservoir evaporation (ERes) was 3.9, 4.2, 4.5, and 2.7 mm d−1 for this 4-month period and the total modelled ERes was 455.8 mm. The developed Kpan function was validated for the same period in 2017 and yielded an R2 value of 0.68. This study proposes an applicable method for calculating evaporation based on pan measurements in Alqueva Reservoir, and it can be used to support regional water management. Moreover, the methodology presented here could be applied to other reservoirs, and the developed equation could act as a first evaluation for the management of other Mediterranean reservoirs.

Digital Twins (DT) can be exploited to improve Collective Irrigation Systems (CIS) performance and be fundamental for decision-making. Developing a DT is an enormous challenge with continuous adjustments and learning from the physical system. Agriculture represents one of the most water demanding sectors, and changing from gravity to pressurised water distribution turning the efficient use of water and energy as one of the main purposes of managing pressurised CIS. The DT is created based on field and laboratory tests, a systematic application of hydraulic modelling, water balance, energy balance and performance indicators. The data connection between the physical system and the DT and data advanced analytics provides a means to the operational setting, optimising, studying scenarios, and adapting to external changes of the pressurised CIS. In this paper, the authors propose a methodology to build a DT of a primary and secondary pressurised CIS network to evaluate water use efficiency, global energy efficiency, pumping facilities efficiency and energy inefficiency associated with water losses. A preliminary application to Block 4, a pressurised subsystem of Odivelas CIS, is presented in Southern Portugal. It was possible to ascertain the great potential of the physical twin -digital twin set to understand system processes, the corrective measures, the priority of maintenance and management decision of the pressurised collective irrigation system. This formulation is a good way to move towards smart water management in CIS.

Abstract. Alqueva Reservoir is one of the largest artificial lakes in Europe and is a strategic water storage for public supply, irrigation, and energy generation. The reservoir is integrated within the Multipurpose Alqueva Project (MAP), which includes almost 70 reservoirs in a water-scarce region of Portugal. The MAP contributes to sustainability in southern Portugal and has an important impact for the entire country. Evaporation is the key component of water losses from the reservoirs included in the MAP. To date, evaporation from Alqueva Reservoir has been estimated by indirect methods or pan evaporation measurements. Eddy covariance measurements were performed at Alqueva Reservoir from July to September in 2014 as this time of the year provides the most representative evaporation volume losses in a Mediterranean climate. This period is also the most important for irrigated agriculture, and is therefore the most problematic part of the year in terms of managing the reservoir. The direct pan evaporation approach was first tested and compared to eddy covariance evaporation measurements. A relationship was then established based on a pan coefficient (Kpan) multivariable function by using the identified governing factors: air temperature, relative humidity, wind speed, and incoming solar radiation. The mean Kpan for the period from June to September 2014 was 0.59, and the modelled mean daily reservoir evaporation in June, July, August, and September was 3.9 mm d−1, 4.2 mm d−1, 4.5 mm d−1, and 2.7 mm d−1, respectively. The total estimated reservoir evaporation for this 4-month period was 455.8 mm. The correlation between the estimated evaporation and the measured EC evaporation had an R2 value of 0.7. The developed Kpan function was validated for the same period in 2017, and yielded an R2 value of 0.68. This study provides an applicable method for calculating evaporation based on pan measurements in Alqueva Reservoir, which can support regional water management. Moreover, the methodology presented here could be applied to other reservoirs, and the developed equation for Alqueva Reservoir could act as a first evaluation for the management of other Mediterranean reservoirs.

O texto deste artigo foi submetido para revisão e possível publicação em agosto de 2016, tendo sido aceite pela Comissão de Editores Científicos Associados em setembro de 2016. Este artigo é parte integrante da Revista Recursos Hídricos, Vol. 37, Nº 2, 65-78, outubro de 2016. © APRH, ISSN 0870-1741 | DOI 10.5894/rh37n2-cti3 RESUMO: O artigo faz uma apresentação breve do sistema de supervisão e controlo (SCADA) desenvolvido para as redes primária e secundária de canais do Aproveitamento Hidroagrícola de Idanha-a-Nova, já instalado e calibrado, dando uma atenção muito especial ao desenvolvimento e calibração dos controladores de caudal para comportas associadas ou não a soleiras descarregadores.Os controladores de caudal desenvolvidos para o SCADA permitem o cálculo do caudal para todas as situações de funcionamento das comportas, garantindo a continuidade das soluções nas passagens do escoamento tipo descarregador para tipo comporta e da situação de ressalto livre para ressalto parcial ou totalmente afogado, em ambos os sentidos. O coeficiente teórico de vazão usado para iniciar o algoritmo de vazão geral foi ajustado no campo com recurso a estimativas de caudal realizadas com dois tipos de caudalímetros e para duas aberturas diferentes de cada comporta e/ou dois regimes permanentes para cada uma das instalações.Foram usados dois tipos de caudalímetros, ambos transdutores acústicos baseados no efeito de Doppler, um fixo no rasto dos canais e o outro portátil e montado numa plataforma flutuante. O artigo faz também uma apresentação breve dos caudalímetros usados, apresenta os resultados das medições de caudal efetuadas e ainda os valores corrigidos para os coeficientes de vazão.