Although the overall hydromorphological quality of the rivers in the surveyed part of the Salaca basin is good and high,…
This summer the LIFE IS SALACA project carried out extensive studies in the Salaca River and its tributaries Korģe, Korģīte, Svētupe, Jaunupe, Glāžupe, Jogla, Iģe and Pužupe. The survey work covered approximately 103 km of river length. Every meter has been paddled or walked, and several weeks in total have been spent in the rivers, summarizing in 167 field protocol of the new harmonized approach, which includes the necessary data to calculate the river quality assessment. An assessment of the hydromorphological quality of the rivers has now been carried out and the necessary management measures to improve the hydromorphological quality have been defined. In the coming months, work on the ecological and habitat quality assessment of the rivers will be carried out.
One of the most important river characterization indices is the Habitat Quality Assessment (HQA). It describes the environmental diversity associated with natural environmental features such as tree roots, different types of mosses, vegetation structure, macrophyte diversity, etc. Higher HQA index indicates higher hydromorphological quality of the river.
In Salaca River the average HQA index value is 61, which corresponds to high quality. Overall, the best quality is found in the middle sections of the river, between Rozēni and Mūrnieki. In the lower sections, near Salacgrīva, the quality starts to decline, which can be mainly explained by the impact of human activities. The highest hydromorphological quality in the Salaca is in the middle section upstream of the Mērnieki and near Rozēni, reaching 78 and 76 points.
In the Svētupe River, the average HQA index value is 68 points, which corresponds to a high quality class. The highest hydromorphological quality is found in the section of the Svētupe between Kuiķele and Lauvas, where it reaches as high as 98 and 92 points, corresponding to the reference level of the Latvian rivers. Downstream of the Jaunupe, the hydromorphological quality of the Svētuupe is significantly lower than in the middle sections, with an average of 53 points, which corresponds to good quality.
In the natural section of the Korģe River the average HQA index value is 69 points. In the straightened section, the hydromorphological quality of the Korģe River is good, with average HQA value of 51 points, indicating the good self-renewal capacity of the river.
The Jaunupe River, which is an artificial channel and nowadays is naturalized, has a generally lower hydromorphological quality than the other natural rivers in the Salaca River basin. Jaunupe River has an average HQA index value of 58, which corresponds to good hydromorphological quality and is also close to the high quality class. In two sections, the HQA index values are 66 and 63, corresponding to high hydromorphological quality.
In the lower sections of the Iģe River, the hydromorphological quality is excellent: the average HQA index value is 80 points, reaching 100 points near the estuary. The only threats to the quality of the lower sections of the river are the remains of the mill dam and beaver activity.
The HQA index value for the Glāžupe River ranges from 32 points, that indicates average quality, to 87, that indicates high quality, because river includes both natural and hydroelectric and dam-altered river sections, which also affects the assessment of hydromorphological quality. The average HQA of the natural sections of the Glāžupe River is 68 points.
In the Jogla River, the average HQA index value is 72 points. Upstream the river impact of human activities increases rapidly and the hydromorphological quality decreases. In the Pužupe River, the average HQA index value in its natural sections is 66, which corresponds to high quality, and in its modified sections 42, which corresponds to average quality. Apparently, the natural hydromorphological potential of the river is too low to allow the river to self-renew. The average HQA index value of the Korģīte River is 69 points, which corresponds to a high quality class.
In general, the highest hydromorphological quality is observed in medium-type rapid rivers, while small and large rivers, regardless of their gradient, have a slightly lower hydromorphological quality. In the Jaunupe River, even though the channel has been naturalized, the hydromorphological quality is lower than in the other observed rivers.
