# Multidimensional Assessment of Lake Water Ecosystem Services Using Remote Sensing
## 1 Introduction  
Ecosystem services are defined as the many benefits humans obtain from ecosystems. These include provisioning services such as food and water; regulating services such as flood and disease control; supporting services such as biodiversity maintenance and habitat preservation; cultural services such as entertainment and landscape aesthetics [1]. The concept of 'ecosystem services assessment' has been regarded as a promising way to describe the situation of ecosystem services [2], scale natural resources storage [1, 3, 4, 5], manage ecological properties [6, 7], support natural resources-related policymaking [8, 9, 10], including freshwater [11, 12, 13]. As one of the primary provisioning services, water provisioning has become a focus because of its economic and social importance and the increasing scarcity. Freshwater is becoming scarce worldwide with the rapidly growing population, developing industries, burgeoning agriculture, and increasing consumption [14, 15, 16, 17, 18]. Climate change and the growing demand for freshwater to support industrial and agricultural development have worsened the situation, and the population suffering from water scarcity has been increasing during the past decades [19, 20]. Some quantitative indicators mapping the capacity of nature to provide water for human beings were created in quantitative assessment of water provisioning ecosystem services, such as the freshwater provisioning index for humans [21], and the water security index [22]. Freshwater scarcity not onlyimpedes economic development and triggers food crises, but also threatens human health since it is directly associated with food quality, energy, and environmental security. To cope with the population explosion and the resulting water shortage, a large variety of ecosystem services related to water resource management have been addressed by assessments [23; 24; 25]. Economic methods have been flourishing since they were adopted by [PERSON] [13; 26; 27; 28; 29; 30], which focus on the economic benefits of ecosystem services and scale it with monetary value. Energy-based methods emerged to mitigate the inaccuracy caused by converting the ecosystem contribution to currency because economic market mechanisms do not always ensure the conservation of ecosystem services [31; 32]. Investigators attempted to regard ecosystem services as a counterpart of energy flows, such as solar energy [33; 34]. We adopted the material-based method, which is based on the theory that humans consume ecosystem services via natural resource materials from the ecosystem, such as food, water, wood, oxygen, clean air [2; 35; 36]. We believe that the process of transferring ecosystem services to humans benefits through some specific carriers. For example, the cropland ecosystems provide food provisioning services, while humans can only obtain and consume this service via obtaining food such as corn and potatoes. Therefore, the weight of the food generated in the cropland ecosystem, which could be measured directly, reflects the amount of food provisioning services [5]. Similarly, human beings enjoy water provisioning services provided by natural hydrological systems via accessible water. Therefore, water storage in nature can be used to scale water provisioning services. The capability of remote sensing to perform synoptic, spatially continuous, and frequent observations resulting in large data volumes and multiple datasets at varying spatial and temporal resolutions contributed to spatially explicit ecosystem services assessment [2; 37; 38; 39; 40]. Compared with the traditional ecosystem services research based on statistical data, remote sensing data can map the spatial distribution of natural resources, mitigating the limitations resulting from administrative boundaries [41; 42; 43]. However, sound scientific information is critical for making effective environmental policies [44]. Scientific results should have a scalable maturity that makes them available to the decision-making process.