Saving Water in Irrigation

A. Vargas, R. Hogeboom & A. Hoekstra

Background

 

Irrigation and crop production are closely related. Irrigation is used to satisfy the water requirements of crops and helps to achieve high productivity levels. However, irrigation is also the source of several negative environmental impacts such as the depletion and pollution of freshwater resources. To reduce these negative impacts, saving water in irrigation is imperative.

According to the Eurostat, in Europe, the agriculture accounts for 45% of the freshwater withdrawals, most of which is used to produce crops. The differences in irrigation water use vary greatly across European countries. Figure 1 provides a picture of the share of irrigated areas per region in the EU. In southern European countries, agriculture claims approximately two thirds of the total. Here, crops often rely on full irrigation. For the more water-rich countries on the other hand, supplementary irrigation might suffice.

This study assesses the potential for water savings in irrigation and how plausible achieving these savings are in the European context. Through an extensive literature review and drawing on stakeholder input, we developed a number of dominant narratives about crop production in Europe. Each narrative proposes a certain perspective on agriculture and water use. We assess how these narratives influence the use of water for irrigation,  how consistent they are, and what possible trade-offs may emerge between them.  

 

Figure 1. Share of irrigated areas in utilised agricultural areas (UAA). Source: Eurostat (online data code: ef_poirrig).

 

How can we measure water savings?

 

Irrigation is one of the main drivers of water scarcity. Water scarcity is defined by the European Commission as a recurrent imbalance that arises from an overuse of water resources, caused by consumption being significantly higher that the natural renewable availability. Note that the focus is on consumption, rather than abstraction of water. These are different concepts, as water abstracted might, at least in part, be returned to natural water bodies, whereas consumed water is lost from the system for other uses. The water footprint measures the water that is consumed for a particular purpose, and it therefore a suitable concept in discussion on saving water and reducing water scarcity.

There are many studies that have calculated the water footprint of crop production and which have proposed reduction measures. Water footprint in this context is defined as the crop water use divided by the yield (or the inverse of water productivity). Either way, water savings can thus be accomplished by either increasing the yield and/or reducing crop water use, including water losses or other non-productive water flows at the field level, such as evaporation from the soil surface that is wetted during irrigation but that does not benefit the plants. Figure 2 illustrates the water flux related to crops.  

 

Figure 2. Water flux. Green soil mosture corresponds to the water obtained via precipitation. Source: Chukalla et al. 2015 (see related work below).

 

Different agricultural management practices are associated with a reduction on the water footprint. Drip irrigation and mulching are examples of such, to name a few. Figure 3 displays the potential reductions on the water footprint driven by different management practices. However, the utilisation of one over another is dependent on the narrative behind.

 

Figure 3. Change in water footprints in different management practices. SSD stands for sub-surface drip, FI for full irrigation, DI for deficit irrigation, NoML for mulching practice, OML for organic mulching and SML for synthetic mulching. Source: Chukalla et al. 2015 (see related work below).

 

Towards narratives that help save water

 

There are different narratives for crop production and each one approaches water savings in different ways. Crop production is a mean to achieve, for example, food security and renewable energy generation. Also, it can both influence and be influenced by the state of the environment. The standpoint selected dictates the way in which water for irrigation can be saved.  

In the EU, the different narratives promote different courses of action and, with them, different strategies to save water in irrigation. The main narratives regarding crop production within the territory gravitate around food security, competitiveness in the global market, fair and sustainable diets, low carbon and circular economy, and technology and efficiency. Each is driven by different objectives and gives water a different role. For example, from a food security perspective, water is a resource to utilise and water savings are approached through sustainable intensification characterized for a ‘more crop per drop vision’. Following a different narrative, in the context of fair and sustainable diets, water is a resource to protect and water savings are approached through extensification, which follows a ‘less drop per crop’ vision. The different narratives therefore employ different management strategies which directly affects the water saving potential, and have different implications for water and its interconnected domains.

 

Work in Progress

 

We are currently analysing the consistency and plausibility of the different narratives in terms of feasibility, viability and desirability. During the upcoming months, we will provide the complete result of our study. Stay tuned!  

 

Related Work

 

Teams Involved