Agricultural impacts of sustainable water use in the United States

Governance measures such as restrictions on groundwater pumping and adjustments to sectoral water pricing have been suggested as response strategies to curtail recent increases in groundwater pumping and enhance sustainable water use. However, little is known about the impacts of such sustainability strategies. We investigate the implications of such measures, with the United States (U.S.) as an example. Using the Global Change Analysis Model (GCAM) with state-level details in the U.S., we find that the combination of these two governance measures can drastically alter agricultural production in the U.S. The Southwest stands to lose upwards of 25% of their total agricultural production, much of which is compensated for by production increases in river basins on the east coast of the U.S. The implementation of future sustainable water governance measures will require additional investments that allow farmers to maximize production while minimizing water withdrawals to avoid potentially detrimental revenue losses.

Game-based education promotes sustainable water use

In this study we estimate the impact of a game-based educational program aimed at promoting sustainable water usage among 2nd-4th grade students and their families living in the municipality of Lucca, Italy. To this purpose we exploited unique data from a quasi-experiment involving about two thousand students, one thousand participating (the treatment group) and one thousand not participating (the control group) in the program. Data were collected by means of a survey that we specifically designed and implemented for collecting students' self-reported behaviors. Our estimates indicate that the program has been successful: the students in the program reported an increase in efficient water usage and an increase in the frequency of discussions with their parents about water usage; moreover, positive effects were still observed after six months. Our findings suggest that game-based educational programs can be an effective instrument to promote sustainable water consumption behaviors in children and their parents.

Who may use scarce water? An expedition into the normative basis of sustainable decision-making norms for sustainable water use

Water is becoming an increasingly contested resource. Today, the sustainability of water use is assessed with different indicator frameworks that usually refer to the Sustainable Development Goals (SDGs) or other norms. Classifying international norms and the subsequent indicators for assessment according to their legitimacy will increase the practical relevance of assessment results. The classification will enable addressees to differentiate between mandatory obligations in water management and additional more ambitious targets for decisions on sustainable water distribution. This study presents 11 standards for sustainable water distribution which have been classified based on legitimacy and specificity. A literature review identified relevant international norms that were subsequently classified. Suggestions for the implementation of the standards and priorities in assessment methods are discussed. Through the new set of standards, assessment results can transparently be communicated to policymakers, NGOs and business and support them to identify their obligations for sustainable water use.

How would irrigation enhance the global BECCS potential in view of sustainable water use?

<p>Bioenergy with carbon capture and storage (BECCS) plays a critical role in many stringent scenarios targeting the 2°C goal. Although irrigation is considered a promising way to enhance BECCS potential while reducing the land requirement, it is still unknown where and to what extent it can enhance the global BECCS potential in view of sustainable water use. Based on integrated hydrological simulations, we found that sustainable irrigation without intervention in water usage for other sectors and refrain from exploiting nonrenewable water sources enhanced BECCS potential by only 5–6% (much smaller than 60–71% for unlimited irrigation) above the rainfed potential by the end of this century. Nonetheless, it adds limited additional water withdrawal (166–298 km<sup>3</sup> yr<sup>-1</sup>, corresponding to only 4–7% of the current total withdrawal) compared to that with unlimited irrigation (1392–3929 km<sup>3</sup> yr<sup>-1</sup>, corresponding to 35–98% of the current total withdrawal).</p>

Worldwide water constraints on attainable irrigated production for major crops

<p>Currently, irrigation withdrawals are resulting in groundwater exploitation and unmet ecosystem water requirements. However, to achieve worldwide food security, there is a need to focus on sustainable intensification of crop production. This requires a more sustainable use of water for irrigated croplands. Our presentation focuses on quantifying attainable wheat, maize, rice and soybean production on currently irrigated cropland under sustainable water use. Attainable production accounts for increases in nutrient application, while limiting irrigation withdrawals to renewable water availability and without compromising river ecosystem water requirements.</p><p>Attainable crop production was quantified using a newly developed two-way coupling between the VIC hydrological model (Droppers et al., 2020) and the WOFOST crop model (Wit et al., 2019). This VIC-WOFOST model framework comprehensively simulates biophysical processes related to water availability and crop growth under water and nutrient limitations. Our results indicate that worldwide crop nitrogen uptake should increase by 20%, to achieve production gap closure. However, worldwide irrigation withdrawals should decrease by more than a third in order to ensure sustainable water use. Under these constraints, decreases in attainable irrigated yields of 5% are expected (14% decrease due to water constraints, 9% increase due to increased nutrient availability). Moreover, achievable irrigated crop production in the extensively irrigated croplands of north-eastern China, Pakistan and north-western India would be reduced by up to a third.</p><p>In addition we explored the impact of atmospheric CO2 enrichment on worldwide attainable irrigated production using VIC-WOFOST. Increased atmospheric CO2 concentration increases crop assimilation and decreases crop transpiration. Initial results show that these effects may offset the unsustainable water withdrawals and increase attainable irrigated yields.</p><p><em>References:</em></p><p><em>Droppers, B., Franssen, W. H., Van Vliet, M. T., Nijssen, B., & Ludwig, F. (2020): Simulating human impacts on global water resources using VIC-5. Geoscientific Model Development, 13(10), 5029-5052, https://doi.org/10.5194/gmd-13-5029-2020</em></p><p><em>de Wit, A., Boogaard, H., Fumagalli, D., Janssen, S., Knapen, R., van Kraalingen, D., ... & van Diepen, K. (2019): 25 years of the WOFOST cropping systems model. Agricultural Systems, 168, 154-167, https://doi.org/10.1016/j.agsy.2018.06.018.</em></p>