Implementing environmental flows (e-flows) is crucial for protecting river ecosystems but often competes with water needs for small-scale agriculture. Understanding these trade-offs is essential for effective water management. We employ holistic modeling to explore the socioecological impacts of e-flows on agriculture along the lower Great Letaba River. Our approach uses conceptual impact pathways and quantitative models to account for smallholder water use, forecasting outcomes under varying river flow conditions. Our findings reveal that the irrigation water demand of small-scale agriculture amounts to only one-tenth of the required e-flow volume. However, farmers face increasing crop water gaps—shortfalls in available water for irrigation—especially during the dry season, which jeopardizes agricultural sustainability as e-flow needs persist. Addressing this challenge may require upstream water flow supplementation, though it would necessitate restricting current upstream water use. We also introduce a robust decision-making model, integrating expert knowledge and Monte Carlo simulations, to assess e-flow management options under uncertainty. By extending the e-flow concept to include the needs of vulnerable farming communities, our model provides decision-makers with an accessible tool for balancing ecological and agricultural demands, even when precise data are unavailable.

中文翻译：

---

平衡生态系统可持续性和灌溉小农农业：水资源管理的建模方法


实施环境流 （e-flows） 对于保护河流生态系统至关重要，但往往与小规模农业的用水需求相冲突。了解这些权衡对于有效的水资源管理至关重要。我们采用整体建模来探索电子流对大莱塔巴河下游农业的社会生态影响。我们的方法使用概念影响路径和定量模型来解释小农户的用水情况，预测不同河流流量条件下的结果。我们的研究结果表明，小规模农业的灌溉用水需求仅为所需 e-flow 体积的十分之一。然而，农民面临着日益严重的作物缺水问题，即可用于灌溉的水资源短缺，尤其是在旱季，由于电子流需求持续存在，这危及农业的可持续性。应对这一挑战可能需要上游水流补充，尽管这需要限制当前的上游用水。我们还引入了一个稳健的决策模型，整合了专业知识和蒙特卡洛模拟，以评估不确定性下的 e-flow 管理选项。通过扩展 e-flow 概念以包括弱势农业社区的需求，我们的模型为决策者提供了一个可访问的工具，即使在无法获得精确数据的情况下，也可以平衡生态和农业需求。