**1. Introduction**

River health is defined as follows:


River health consists of both ecological and human values, as shown in **Figure 1**, and is mostly dependent on river condition, which is measured mostly by a large variety of qualitative indices (poor-to-excellent scaling system) as seen in Ladson et al. [5], Hill et al. [6], Gordon et al. [7], Acreman and Ferguson [8], and Atazadeh et al. [3]. Physicochemical indices are the most common indices for lotic water, for example, in the U.S. as seen in Toxic and Priority Pollutants Under the Clean Water Act [9], which are extended to Chemical, Microbiological, Whole Effluent Toxicity, Radiochemical,

**Figure 1.**

*Ecological and human value contribution to river health as modified from [3, 4].*

Industry-Specific and Biosolids [10]. However, these proved inadequate in achieving full spectrum protection [11, 12].

The first to point out that organic matter concentration areas in streams attract invertebrates was Hynes in [13] based on the previous works [14, 15] on the bottom fauna distribution and quantity. This was followed by the River Continuum Concept where "*the structural and functional characteristics of stream communities are adapted to conform to the most probable position or mean sate of the physical system*" [16], the framework for a spatiotemporal hierarchical classification system "*among and within stream systems*" [17] and the collection of articles in Boon and Raven [18]. These are some of the cornerstones that led to the employment of bioindicators, biomonitoring, and bioassessment. Biological indicators (bioindicators) are defined as "*an organism (or part of an organism or a community of organisms) that contains information on the quality of the environment (or a part of the environment)*" [19]. Biomonitoring is "the systematic use of living organisms or their responses to determine the condition or changes of the environment" [20]. Bioassessment is defined as "*an evaluation of the* 

*Monitoring of Rivers and Streams Conditions Using Biological Indices with Emphasis on Algae… DOI: http://dx.doi.org/10.5772/intechopen.105749*

*condition of a waterbody using biological surveys and other direct measurements of the resident biota in surface water*" [21].

Consequently, biological indicators fill in the gaps left by physiochemical indices as being more integrative [22] and range from lower trophic-level organisms (e.g., algae or benthic macroinvertebrates) all the way to upper trophic-level species (e.g., fish and mussels). These, combined with river geomorphological and hydrological indices [7], form a more dependable framework upon which river health assessment can rely [23]. Algae entered the phase of scientific study well over a hundred years ago and its connection with riverine environmental condition started in 1908 [24–30].
