Sustainable water consumption is one of the issues covered in the context of sustainable development (UN, 2018) within the Sustainable Development Goals of “Clean Water and Sanitation” and “Responsible Consumption and Production”. As water is a finite source on Earth and its renewal rate mostly depends on human use (UN,2015), it is essential to teach individuals how to use water sustainably within the context of education for sustainability (Benninghaus, Kremer, & Sprenger, 2017). To achieve this, the concept of hidden use of water is also an important aspect since most of our water consumption habits are correlated with our hidden use of water. Hidden use of water is defined as the amount of water used in agricultural and industrial products (National Geographic, 2014). Thus, individuals shall have background knowledge on their consumption for monitoring their sustainable water use. As stated by Reinfried (2006), if individuals do not have background knowledge on their consumption, they would not possibly monitor their water consumption behaviour sustainably.

When the accessible literature on the hidden use of water was examined, it is seen that limited number of studies investigated this concept. For example, Fremerey, Liefländer and Bogner (2014) conducted a survey related to the students’ conceptions of drinking water. They reported that only a minority of the students had a proper understanding on hidden use of water. In a similar manner, Benninhaus, Kremer & Sprenger, (2017) examined the students’ notion of virtual water and found that substantial number of participants had lack of understanding of virtual water as well as the water consumption in the production of chains.

In this study, we aimed to explore Turkish middle school students’ understanding of hidden use of water and their action strategies for sustainable water use. Determining their action strategies may also provide us hints about their notion on the context of hidden use of water. As there are a limited number of studies, this study may help enrich the literature so that further studies can be encouraged on this subject. On the other hand, this topic is not covered yet in Turkish national science curriculum. Therefore, the findings of the study may provide some insights to the ones who does not include the terms of hidden use of water in their curricula yet. Correspondingly, the research questions of this study were as follows:

RQ1: What are the understandings of eight-grade students on their hidden use of water?

RQ2: What are the action strategies of eight-grade students for sustainable use of water?

Qualitative research design was used for this study since we intended to acquire in-depth information from the participants about their notion on the use of water. Specifically, basic qualitative research was chosen since we tried to understand how students interpret the phenomenon (Merriam, 2009), in this case, hidden-use of water. Moreover, we also intended to explore “what meaning they attribute to their experiences” (Merriam, 2009, p. 23). We purposefully selected different provinces to reflect habits for water-use depending on different cultural perspectives. Correspondingly, four districts were selected from Ankara in Turkey with purposeful sampling method. Then, convenience sampling method was used to determine schools. Accordingly, a total of 358 eight-grade students (44.7% male, 52.8% female, 2.5% missing) from five schools were participated into the study. Among them, six students were interviewed to elaborate their notion of hidden-use of water. The written task and semi-structured interview were developed by the researchers to evaluate students’ understanding of hidden use of water and their action strategies for sustainable use of water. The task was composed on four questions. The first two questions were multiple-choice items related to the hidden-use of water. Former question was intended to understand whether students could be able to differ productions (i.e. tomatoes, chocolate, rice, hamburger) that requires much water than the others. Latter question was asked to identify if students differentiate sustainable water consumption behaviour among the alternatives. The remaining two questions were extended response essay items associated to action strategies. These questions were prepared based on a text given to the students about the percentages of water usage in Turkey. Then, it was asked to write suitable action strategies. In terms of data analysis, we used descriptive statistics for multiple-choice items. For the essay questions, we used content analysis. Inductive coding was used to determine codes. To ensure transferability of the study, purposive sampling method was used. In terms of dependability, extended response essay items were coded by another researcher. Inter-coding agreement was calculated and percentage of agreement for the extended response essay items were 99.12% and 86.36% respectively. Besides, intra-coding was also implemented by the researcher. Some precautions related to external reliability such as reporting researcher’s bias, selection of informant participants, description of the conditions, were considered. Last, ethical permission was also obtained from the national ministry of education to ensure that there would be no harm to the participants during the study.

To examine their notion on the hidden-use of water, two questions were asked. The frequencies revealed that most of the students had lack of understanding. For example, 35.8 % of the students responded that eating less hamburger is not one of the examples for sustainable water use. Besides, more than 80% of the students named rice and tomatoes as food requiring much water than chocolate and hamburger. These responses can be indicators for limited understanding. They may imagine direct-use of water during production. To elaborate their understanding, six students (3 males, 3 females) were interviewed. They reported that they have not heard about the term “hidden-use of water” before. Moreover, when we asked in which steps water is consumed during hamburger production, responses mainly derived from direct-use of water (i.e. people irrigate crops, animals drink water). They did not include the wastewater as well as the water for growing animal feed. These responses are compatible with findings from the written task. To determine students’ action strategies, two extended response essay items were given with a text. The text explains water consumption habits of Turkey in terms of percentages for agricultural, industrial, and domestic use. Firstly, students were asked to share their action strategies. The most-frequently actions written were related to reducing domestic use of water. Only 2.79% of the respondents suggested strategies to reduce hidden-use of water. The latter question was about what they would do if they were a governor. Similarly, majority of the responses were about the regulations for direct-use of water. Agricultural (3.35%) and industrial (0.30%) regulations were in minority. These findings were compatible with the literature (Fremerey et al. ,2014; Benninhaus, et al., 2017). These results implied that lack of understanding on the hidden-use of water could be a limitation to raise informed-decision makers for the future.

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