Spatial and Temporal Trends in the Water Quality of Huluka River, Ethiopia: An Assessment Using Selected Physicochemical and Biological Methods

Alemayehu, Negassa Emana (2016) Spatial and Temporal Trends in the Water Quality of Huluka River, Ethiopia: An Assessment Using Selected Physicochemical and Biological Methods. PhD thesis, Addis Ababa University.

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Abstract

Spatial and temporal trends in the water quality of Huluka River were assessed using physicochemical parameters, physical habitat assessment and biotic indices/metrics. The assessment involved insitu measurements and collection of water samples on monthly basis from June to December, 2014 as well as biological (epilithic diatoms and benthic macroinvertebrates) sampling and habitat survey in June and December from nine sampling sites coded S1 to S9 along the river using standard procedures. Soluble reactive phosphorus, nitrate-N, chemical oxygen demand and cadmium revealed increased water quality deterioration at downstream sites (i. e. S6, S7, S8 and S9) and during wet season. Conductivity, pH and dissolved oxygen also indicated increased water quality problems at the downstream sites, S7 and S6, respectively in both seasons. Physical habitat evaluation scores varied from 48% at S4 to 75% at S1 and relatively lower scores were recorded at S3, S4 and S6 in both monthes. A total of 115 diatom species belonging to 21 genera with Achnanthes, Gopmhonema, Navicula and Nitzschia being the most common ones were identified from the samples collected of which 82 species representing 17 genera and 71 species in 18 genera were collected in June and December, respectively. Gomphonema parvulumn (47%), Nitzschia palea (30%) and Acnanthidium minutissimum (25%) were the most dominant species collected in June while Nitzschia liebetruthii (80%), Acnanthidium minutissimum (70%) and Nitzschia amphibian (61%) dominated the epilithic diatom communities collected in December. A total of 22 families of benthic macroinvertebrates were identified from the samples collected of which 17 and 16 families represented samples collected in June and December, respectively. Hirudinae (84%), Hydropsychidae (65%) and Chironomidae (52%) were the most dominant taxa collected in June while Baetidae (74%), Caenidae (66%) and Hydropsychidae (61%) dominated the benthic macroinvertebrate communities collected in December. The spatial and temporal variations in most biotic indices/metrics determined including community loss index, saprobic index, trophic diatom index, % of Ephemeroptera and Trichoptera, %Diptera, Ephemeroptera and Trichoptera-Chironomidae ratio, the new Ethiopian scoring system and Functional Feeding Groups) also indicated Huluka River water quality deterioration mainly at downstream sites as it flows through Ambo town and in June. Taxa richness and diversity indices of the two assemblages also indicated a relatively more deteriorated water quality at the downstream sites. Results of Cluster and Canonical Correspondence Analyses also indicated water quality deterioration at downstream sites mainly S7 and S8 during both sampling monthes. Pressure from livestock, poor farming methods, destruction of riparian forest, the discharge of untreated or poorly treated sewage and poor solid waste management were the major environmental stressors identified impacting the water quality of Huluka River.

Item Type:	Thesis (PhD)
Uncontrolled Keywords:	Diatoms, Heavy Metals, Huluka River, Macroinvertebrates, Nutrients
Subjects:	G Geography. Anthropology. Recreation > GE Environmental Sciences Q Science > QD Chemistry Q Science > QH Natural history > QH301 Biology
Divisions:	Africana
Depositing User:	Selom Ghislain
Date Deposited:	19 Jun 2018 13:53
Last Modified:	19 Jun 2018 13:53
URI:	http://thesisbank.jhia.ac.ke/id/eprint/4644

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