Land change simulation for highly water-demanding crops may prove a valuable tool to guide integrated land-and-water management in semi-arid regions facing water scarcity. We explored this premise by mapping and modelling past (1985–2015) and future (2015–2030) orchard development relative to water resources and other factors in Iran. We employed a hybrid GEOMOD-Markov Chain model whereby both the spatial allocation and quantity of orchard development were simulated. By 2030, orchard cover is projected to increase by 20% of its 2015 area, straining limited water resources. To gauge the accuracy of our projection of orchard gain to 2030, we assessed a comparable simulation of orchard gain for 2000–2015 according to the various components the Figure of Merit (FOM) metric. Misses, Hits and False Alarms of simulated orchard gain accounted for 1.84%, 0.45% and 0.74% of the study area respectively over 2000–2015 at a 200-m spatial resolution, for which the FOM was appreciable (15%) given the limited extent of simulated orchard gain and actual orchard cover across the study region (1.2% and 5.3%). With respect to orchard gain, spatial allocation error was more than land-change quantity error at 200-m resolution, at 1.48% and 1.10% of the study area, respectively. Predicting the location of agricultural change remains a priority and challenge for model utility, given scant agricultural footprints in semi-arid regions and their large draw on limited water resources. Results also indicate the importance of incorporating dynamic water availability and demand over the course of agricultural expansion, including shifts in the location preference amongst farmers. The integration of dynamic, agent-based models within our GEOMOD-Markov Chain framework is therefore methodologically appealing, but would adversely increase complexity for policymakers.

高度需水作物的土地变化模拟可能被证明是指导面临缺水的半干旱地区综合水土管理的宝贵工具。我们通过绘制和模拟伊朗过去（1985-2015 年）和未来（2015-2030 年）果园发展与水资源和其他因素的关系来探索这一前提。我们采用混合 GEOMOD-马尔可夫链模型，其中模拟了果园开发的空间分配和数量。到 2030 年，果园覆盖面积预计将增加 2015 年面积的 20%，从而使有限的水资源紧张。为了衡量我们对 2030 年果园收益预测的准确性，我们根据品质因数 (FOM) 指标的各个组成部分评估了 2000-2015 年果园收益的可比模拟。模拟果园增益的未命中、命中和误报分别占 1.84%、0。2000-2015 年间以 200 米空间分辨率分别占研究区域的 45% 和 0.74%，鉴于整个研究区域的模拟果园增益和实际果园覆盖范围有限（1.2 % 和 5.3%）。在果园增益方面，空间分配误差大于200米分辨率的土地变化量误差，分别占研究区的1.48%和1.10%。考虑到半干旱地区的农业足迹很少且大量利用有限的水资源，预测农业变化的位置仍然是模型效用的优先事项和挑战。结果还表明，在农业扩张过程中结合动态水资源供应和需求的重要性，包括农民对地点偏好的转变。动态整合，