**2.1. Annual agricultural crops**

interpretation [18, 19]. Many scientists have attempted to answer the "what," "what level," "for whom," "biological or economic," and "how long" questions of sustainability. However, there is no absolute definition of sustainability, and that it must be viewed within the context of the human conceptual framework, societal decisions on the state of ecosystem to be sustained, and the temporal and spatial scales over which sustainability is to be judged [18]. In

Reporting of water impacts on ecosystems caused by the implementation of bioenergy systems is both variable and incomplete (**Figure 1**). While some assessments include only active human uses such as irrigation and water used in biofuel conversion processes, others include hydrologic processes such as evapotranspiration, infiltration, runoff, and baseflows, which are natural ecosystem processes influenced by human activity (**Figure 2**) [2]. Water limitations may reduce the opportunities to use bioenergy in some ecosystems. However, there are many situations where bioenergy may advance both socioeconomic and sustainable landscape objectives [9, 12]. The objective of good bioenergy management is to keep water flow on

**Figure 2.** Hydrologic processes governing the water cycle and the distribution between desired good water supply, fair

short, this approach is loaded with considerable uncertainty and lack of consensus.

**2. Water impacts of modern bioenergy programs**

the right side of the diagram in **Figure 2**.

116 Energy Systems and Environment

water supply, and poor water supply in ecosystems (From [12]).

The cultivation of conventional annual crops as bioenergy feedstocks affects soil and water resources similar to crop cultivation for food and livestock feed. Water withdrawals and the effects of agrochemicals must be carefully managed to avoid human health impacts, water quality degradation, and damage to ecosystems [20]. As in other agricultural and forestry activities, the adoption of BMPs is crucial to minimizing the risk of water quality impacts and promoting sustainable resource use. Assessing BMPs and their effectiveness further requires defining appropriate water quality expectations, determining what site conditions limit BMP effectiveness, and identifying the specific watershed characteristics and appropriate spatial and temporal scales for assessment [21].
