The water movement of the sewer collectors is of a non-permanent type because of the variation in flow over time. Non-permanent movement in collectors is mathematically modelled by the Saint Venant equations. To solve the equation system, the characteristic method was used, provided that both equations are quasi-linear in the unknown h and Q. Non-dynamic contouring conditions are given by the hydraulic feature of the collectors / tanks located on the collector. Dynamic contour conditions are rendered by the collector-specific equations (river level effluent hydrograph, manoeuvring parameters of the boiler, manoeuvring characteristics at pumping stations, etc.). For the mathematical model implementation, a computational program was developed in the Matlab programming environment (Variation Gradual Collector Program). The program was used to simulate the non-permanent movement in the main sewerage collector “Cacaina” from the sewerage network of the city of Iasi. The simulation of the non-permanent movement was done in two collector evacuation scenarios (gravity and pumping). The analysis of the results obtained for scenario 2 highlights the differential operation of the eight collector sections separated by the side feeders. Simulation of the movement has highlighted the exceeding of the minimum and maximum values of the parameters imposed by the operating rules.

The paper presents the studies and researches on the natural and anthropic risk parameters on the Moldova riverbed in the Soci area, Iasi County. In this area are located hydrotechnical structures for regulation of the riverbed and shore defence for the protection of the undercrossing of the Timisesti-Iasi adduction pipeline. The theoretical study analyzed hydrological risk parameters (especially liquid and solid flows) recorded over the last 30 years. High flow rates have a high hydroclimatic risk for bed and river construction. Anthropogenic risk parameters were manifested in the morphological modification of the minor riverbed of the Moldova River. An important anthropogenic risk is the uncontrolled exploitation of the ballast in the bed and river banks of Moldova. The effects of this risk contributed to the descent of the bed of the bed at an accelerated pace, along with the erosion of the banks. The accumulation of the effects caused by the natural and the anthropic risks led to important morphological changes in the riverbed of Moldova. These modifications have altered the safety state of the construction of the undercrossing of the Timisesti-Iasi adduction pipeline. The result of the hydrological and also human actions was the degradation of the pipelines until their rupture.

An important issue in the design of the main visitable sewer collectors is the hydraulic calculation in permanent movement and non-permanent movement. Some main collectors that can be visited have non-standard flow sections, a situation that complicates the hydraulic calculation. Non-standard flow sections derive from standard sections (circular, ovoid, bell, rectangular and mixed) through natural and anthropogenic degradation processes. The initially designed section changes over time in terms of shape, dimensions and roughness, a situation in which determining the hydraulic parameters becomes very difficult. The research carried out on a series of visitable main collectors revealed that the flow section has geometrically transformed from curved shapes to mixed shapes (curves + right-hand segments).The hydraulic rehabilitation of degraded collectors requires the analysis of flow parameters in the case of geometrically modified sections. The non-standardized flow section can be considered as a “single bed”, or as a “multiple bed”. At the same time, the “single bed” type sections composed of both circular arcs and straight line segments can be hydraulically analyzed with a customized calculation program. The paper presents a model for calculating the geometric and hydraulic parameters of a sewer collector with a non-standard shape and in permanent uniform motion.

The Moldavian Plateau and Plain have few drinking water sources (the case of Iaşi and Vaslui Counties). The main type of fresh water sources are groundwater and surface water. The Moldavian Plateau rural settlements are affected the most by the lack of viable, unpolluted water sources to ensure a volume able to cover the consumers’ demand. The pollution phenomenon induced by the non-availability of rural sewerage systems and also by the settlements’ areas foundation rocks have decreased the groundwater and surface water sources quality parameters. The adduction, transport and distribution networks of water supply systems are affected by the „water loss“ phenomenon. Water management in a transmission and distribution network must correlate the number of water sources, available volume, acceptable quality parameters and inherent water losses from networks with the consumers’ demands. The optimisation of water management in a given geographic space has led to the establishment of „regional water supply systems“. This process relies on the minimisation of water losses. The case study carried out in Iaşi County shows the importance of the regional water supply system development through optimal exploitation of Moldavian Plateau and Plain water sources.