Framework for Assessing Collective Irrigation Systems Resilience to Climate Change—The Maiorga Case Study

Abstract

In order to increase water productivity at the Collective Irrigation System (CIS) level it is crucial to adapt the existing irrigation infrastructure, enhancing water intake at the source, as well as its transport and delivery efficiency. Rehabilitation may involve structural changes and thus, a large capital investment. This investment should be proportionate to the increase in climate resilience associated to different rehabilitation alternatives. A methodology framework was developed to evaluate CIS resilience to climate change considering different rehabilitation alternatives. The assessed components were: (i) crop production systems; (ii) on-farm irrigation systems; and (iii) project rehabilitation alternatives for the conveyance and distribution of the irrigation water from the source to the farmer fields. This framework was applied to the Maiorga CIS, in central Portugal, to test the methodology performance in assessing the impacts of climate change on the supply-demand balance of the proposed rehabilitation alternatives and to evaluate their climate resilience, for the representative concentration pathways, RCP4.5 and RCP8.5, and two time periods, 2041–2070 and 2071–2100. For each scenario, period, and rehabilitation alternative, irrigation requirements at the source (demand) and stream flows (supply) were computed and the supply-demand balance was performed. Projected increases in irrigation water demand varied between 5.5% for RCP4.5/2071–2100 and 35.7% for RCP8.5/2071–2100. For RCP4.5, 11% (2050) and 9% (2080) reductions in irrigation water supply were projected, while for RCP8.5 the reduction ranges between 13% (2050) and 30% (2080). The proposed framework determined that the rehabilitation alternatives considering just one type of water source, without flow regularization and with open channel distribution to the farmer’s field, have proved to be unviable due to low resilience to climate change.

Potential Effects of Climate Change on Agricultural Water Resources in Riyadh Region, Saudi Arabia

“…In SSP5-8.5 for the far future 2100s scenario, the values of Etc are increased to 359, 1034.6, 361.6, 1248.6, 520.2, 880.4, 685, and 422.6 mm/day for wheat, clover, other vegetables, dates, maize, citrus, tomato, and potato, respectively; this increase in Etc is a result of a rise in temperature during the growing season. Various earlier studies of regions with similar arid and semi-arid climatic conditions such as India (Kaushika et al [38]), Egypt (Makar et al [21]), and Ethiopia (Hordofa et al [20]) reached a similar conclusion: in the long run, a slight increase or reduction in precipitation and an observable increase in temperature will result in an increase in crop water requirements, particularly if sowing dates are delayed. Previous findings indicate that crop and irrigation demand may grow in the mid-to long-term, particularly from June to August, since evapotranspiration parallels the temperature behavior in the study area.…”

“…CROPWAT 8 is a set of parts based on the Penman-Monteith technique that combines numerous models for predicting CWR, IWR, and crop scheduling [32]. It is based on the FAO-approved Penman-Monteith method for predicting reference evapotranspiration (ET o ), crop evapotranspiration (ETc), and irrigation water management [21]. It should be emphasized that ETc denotes the amount of water lost to evapotranspiration by the crop, whereas CWR denotes the water quantity to be provided.…”

“…Feng et al [20] demonstrated that climate change was a contributing cause to oscillations in grain output using climate data and grain yield records from 1978 to 2021. Conversely, the authors of [21] reported the losses in irrigation water supplies were expected to reach 9% in the best-case scenario (year 2080). According to Yin et al [22], by 2071-2100, the risks of bivariate drought hazards would have increased 10-fold, owing primarily to increases in heat extremes.…”

Methodologies for Water Accounting at the Collective Irrigation System Scale Aiming at Optimizing Water Productivity

“…CIS are common in many parts of the world, especially in arid and semi-arid regions, where water is a scarce resource and farmers often rely on collective management to optimize water use and minimize conflicts among users [13][14][15]. The assessment of CIS performance is, therefore, an essential primary step toward improving agricultural water use, particularly for making decisions on modernization investments and management changes [16,64,93]. It must encompass both the delivery and the on-farm systems and requires extensive datasets both in time and space.…”

Irrigation Schedule Optimization for Wheat and Sunflower Intercropping under Water Supply Restrictions in Inner Mongolia, China

“…The ISAREG irrigation scheduling simulation model was calibrated, validated, and tested using historical information from 19 years of maize experiments. Furthermore, these statistics were used to establish suitable crop characteristics [21][22][23]. The ISAREG approach was used to determine enhanced irrigation schedules for horticultural crops in Cuba.…”