Irrigation districts play a decisive role in Portuguese agriculture and require the adaptation to the new water management paradigm through a change in technology and practices compatible with farmers’ technical know-how and economic sustainability. Therefore, improvement of water management, focusing on water savings and increasing farmers’ income, is a priority. In this perspective, an applied research study is being carried out on the gravity-fed Lis Valley Irrigation District to assess the performance of collective water supply, effectiveness of water pumping, and safety of crop production due to the practice of reuse of drainage water. The water balance method was applied at irrigation supply sectors, including gravity and Pumping Irrigation Allocation. The average 2018 irrigation water allocated was 7400 m³/ha, being 9.3% by pumping recharge, with a global efficiency of about 67%. The water quality analysis allowed identifying some risk situations regarding salinization and microbiological issues, justifying action to solve or mitigate the problems, especially at the level of the farmers’ fields, according to the crops and the irrigation systems. Results point to priority actions to consolidate improved water management: better maintenance and conservation of infrastructure of hydraulic infrastructures to reduce water losses and better flow control; implementation of optimal operational plans, to adjust the water demand with distribution; improvement of the on-farm systems with better water application control and maintenance procedures; and improvement of the control of water quality on the water reuse from drainage ditches. The technological innovation is an element of the modernization of irrigation districts that justifies the development of multiple efforts and synergies among stakeholders, namely farmers, water users association, and researchers.

Rice irrigation by continuous flooding is highly water demanding in comparison with most methods applied in the irrigation of other crops, due to a significant deep percolation and surface drainage of paddies. The pollution of water resources and methane emissions are other environmental problems of rice agroecosystems, which require effective agronomic changes to safeguard its sustainable production. To contribute to this solution, an experimental study of alternate wetting and drying flooding (AWD) was carried out in the Center of Portugal in farmer’s paddies, using the methodology of field irrigation evaluation. The AWD results showed that there is a relevant potential to save about 10% of irrigation water with a reduced yield impact, allowing an additional period of about 10 to 29 days of dry soil. The guidelines to promote the on-farm scale AWD automation were outlined, integrating multiple data sources, to get a safe control of soil water and crop productivity. The conclusions point out the advantages of a significant change in the irrigation procedures, the use of water level sensors to assess the right irrigation scheduling to manage the soil deficit and the mild crop stress during the dry periods, and the development of paddy irrigation supplies, to allow a safe and smart AWD.

This research was carried out as part of a program for the conservation and improvement of the strawberry tree. Accessions’ prospecting was conducted in different Portuguese provenances. Accessions (204) were identified, and mature fruits were collected in autumn. The sugar contents in the fruit pulp (glucose, fructose, maltose, sucrose) were analyzed by HPLC and the correlation between the average sugar content, climatic classification (Thornthwaite Method and Xerothermic Index), and edaphic characteristics was investigated. The predominant sugar was fructose, which ranged from 7.89 ± 0.55% to 17.01 ± 1.46% (f.w.), respectively, under an Attenuated Thermomediterranean climate at limestone-derived soil and an Accentuated Mesomediterranean climate at schist-derived soil. The lowest sugar contents, linked to a reduction in photosynthesis, were found: (1) in the north, despite soil water availability, due to the low temperature, high precipitation and short photoperiod, particularly during the fruit maturation (autumn); (2) in the south, due to the excessive number of dry days, linked to low soil water availability during the active growth period, particularly at limestone zones prone to water retention. The relationship found between the total sugar content and climate classification by the Xerothermic Index allows to enhance fruit production, advise on the establishment of new orchards and restore natural areas.

This research was carried out as part of a program for the conservation and improvement of the strawberry tree. Accessions’ prospecting was conducted in different Portuguese provenances. Accessions (204) were identified, and mature fruits were collected in autumn. The sugar contents in the fruit pulp (glucose, fructose, maltose, sucrose) were analyzed by HPLC and the correlation between the average sugar content, climatic classification (Thornthwaite Method and Xerothermic Index), and edaphic characteristics was investigated. The predominant sugar was fructose, which ranged from 7.89±0.55% to 17.01±1.46% (f.w.), respectively, under an Attenuated Thermomediterranean climate at limestone-derived soil and an Accentuated Mesomediterranean climate at schist-derived soil. The lowest sugar contents, linked to a reduction in photosynthesis, were found: 1) in the north, despite soil water availability, due to the low temperature, high precipitation and short photoperiod, particularly during the fruit maturation (autumn); 2) in the south, due to the excessive number of dry days, linked to low soil water availability during the active growth period, particularly at limestone zones prone to water retention. The relationship found between the total sugar content and climate classification by the Xerothermic Index allows to enhance fruit production, advise on the establishment of new orchards and restore natural areas.

A presente comunicação apresenta resultados da atividade do Grupo Operacional para a gestão da água no Vale do Lis, desenvolvida no Aproveitamento Hidroagrícola do Vale do Lis (AHVL), um regadio coletivo público localizado no Centro Litoral de Portugal, com cerca de 2000 ha. Compreende aluviossolos modernos, cultivando-se milho-grão, prados e forragens, arroz, pomares, viveiros e hortícolas. Este grupo operacional visa a melhoria da planificação, gestão e uso da água e a modernização sustentável do AHVL, em articulação com a Associação de Regantes e Beneficiários do Vale do Lis . O aproveitamento estrutura-se em nove blocos hidráulicos com funcionamento relativamente independente. A adução ao perímetro é a fio de água através de vários açudes e estações elevatórias (EE), captando-se água do rio Lis, afluentes e valas de drenagem. A rede de distribuição é gravítica em canal, regadeiras e tomadas de água.A monitorização da redes coletiva de abastecimento baseia-se na observação do modo operativo e dos hidrogramas de afluência. Foi efetuada a medição de caudais na entrada dos vários blocos, nas derivações na rede gravítica ou nas EE de reforço, recorrendo-se a molinete electromagnético e ao método secção-velocidade, com observações regulares durante a campanha de rega. As observações foram complementadas com os registos de operação e maneio da rede e os registos contínuos do nível de água nos açudes principais do rio Lis, de Arrabalde e Salgadas. As condições de drenagem e o potencial contributo hídrico para as culturas por ascensão capilar foram avaliadas por medição de nível freático em furos piezométricos com 3 m de profundidade. Foram igualmente registados os consumos de energia nas EE. A monitorização da qualidade físico-química e microbiológica da água de rega e drenagem foi efectuada em pontos de entrada e saída do aproveitamento. A análise físico-química foi efetuada com sonda multiparamétrica portátil e em laboratório. As observações microbiológicas foram efetuadas no período de ponta de estiagem com a colheita de amostras em condições de assépsia para análise em laboratório.Nesta comunicação serão apresentados os resultados da monitorização de 2018 e a sua aplicação no apoio à gestão do sistema. A análise dos resultados permitiu identificar alguns aspectos de constrangimento do sistema, dando informação sobre medidas a adoptar. São exemplo a manutenção e limpeza de canais, auditorias energéticas nas EE e avaliação das condições de fertilização orgânica. O balanço hídrico ao nível dos blocos hidráulicos, baseado em informação hidrométrica, meteorológica e cultural, permitirá aplicar um modelo de integração de informação visando o apoio à gestão da água no aproveitamento. Gonçalves, José Manuel; Nunes, Manuel; Amador, Paula; Filipe, Olga; Ferreira, Susana; Eugénio, Rui; Duarte, Isabel Maria; Teixeira; Marques; Oliveira, Fátima; Gonçalves, Madalena; Damásio, Henrique

The paper presents an approach to modelling water flows interaction in the vadose zone. The study was applied to surface irrigated maize in the Lower Mondego Valley, located in the centre-west of Portugal with 12,000 ha of irrigated area. The study aims at: (i) evaluating the drainage and capillary rise fluxes through the lower boundary of the root zone using the HYDRUS model, and (ii) assessing the impacts of recharge flows due to irrigation and/or originating in the surrounding drainage ditches on the water table using the MODFLOW model. Two different field soil conditions (sandy-loam and silty-loamy) were considered. The parameterization of the unsaturated vadose zone was performed using the Van Genuchten-Mualem equations characterizing the soil hydrodynamics behaviour. Aimed at modelling, field observations included: dynamics of the groundwater table level using piezometer recorders; soil moisture dynamics; meteorological, field irrigation and crop development data. The HYDRUS calibration was performed through adjusting simulated to observed soil water content. Groundwater modelling with MODFLOW was performed using data on aquifer-system geometry, hydrological parameters and the groundwater heads observed. The use of MODFLOW focused the evaluation of recharging flows to the groundwater table consisting in vertical flows from the unsaturated zone (obtained from the HYDRUS), and lateral flows from ditches and the adjacent rice paddies. Drainage flows from water table to ditches and deep percolation to the main aquifer were also evaluated. The application of these two models, adopting an iterative process, allowed to properly simulate the dynamics of water table level variations. The paper presents the comparison between models results and field observation data. In order to minimize irrigation water excess and keeping soil water storage in levels appropriate to obtain maximum yields, a modification of the irrigation schedule is suggested, which is combined with water level control and improvement of surface irrigation performance.