Analyzing human impacts on the quality and quantity of river water

Abstract Human activities endanger the role of rivers as one of the most valuable freshwater sources and essential ecosystem service providers. Dam construction, agriculture, mining, industry, and land-use change can alter river water quality and the seasonal variability of river discharge, thereby deteriorating the ecological status of rivers. This doctoral thesis explores the impact of each of these activities on river water quality and quantity, and suggests new frameworks and indicators which can be used to enhance the understanding of human impacts on rivers. Two case studies presented here investigated the impact of small reservoirs and multiple dam construction — in connection with land-use change — on river flow characteristics in arid/semi-arid and Mediterranean climates (Iran and Turkey). A third case study analyzed the impact of mining on river water quality in a pristine river in an Arctic region (Finnish Lapland) and proposed a new indicator to enhance the monitoring system. This thesis brings awareness to the potential impact of multiple activities on river systems and delivers new methods to quantify those impacts with minimum cost and maximum effectiveness. The framework presented here could be used by researchers and authorities to monitor river health in different climates.Tiivistelmä Ihmistoiminnan vaikutukset jokisysteemeihin vaarantavat niiden aseman tärkeinä makean veden lähteinä ja ekosysteemipalvelujen tarjoajina. Jokien padottaminen, maatalous, kaivostoiminta, teollisuus ja eri maankäyttömuodot vaikuttavat jokivesien laatuun ja virtaamiin, täten muuttaen niihin liittyvien ekosysteemien tilaa. Tämän väitöskirjatyön tarkoituksena on tutkia näiden tekijöiden vaikutusta vedenlaatuun ja määrään sekä tarjota uusia näkymiä ja työkaluja, joiden avulla pystytään lisäämään tietoa ja ymmärrystä ihmistoiminnan vaikutuksista jokisysteemeihin. Tulokset saatiin kolmen Case-tapauksen avulla, joissa kahdessa tarkasteltiin lukuisten pienpatoaltaiden ja itse patojen rakentamisen sekä maankäytön muutoksen vaikutusta jokien virtaamien dynamiikkaan kuivalla/puolikuivalla sekä välimerellisellä ilmastovyöhykkeellä (Turkki ja Iran). Kolmas case-tapaus käsitteli kaivostoiminnan vaikutuksia luonnontilaiseen jokeen ja sen vedenlaatuun arktisella alueella (Suomen Lappi). Vaikutuksia tarkasteltiin käyttäen jatkuvatoimisesti mitattua sähkönjohtavuutta indikaattorina vedenlaatumuutoksille. Tämä väitöstyö lisää tietoisuutta monien eri toimintojen vaikutuksista jokisysteemeihin ja tarjoaa uusia keinoja määrittää näitä vaikutuksia kustannustehokkaasti. Työssä luotua kehikkoa voidaan käyttää tutkijoiden ja viranomaisten toimesta monissa eri ympäristöissä ja ilmasto-oloissa

Assessing the impacts of artificial groundwater recharge structures on river flow regime in arid and semi-arid regions

In dry and semi-dry climate, Artificial Groundwater Recharge Structures are used for flood control and managed aquifer recharge. These damps basin runoff response decrease the maximum flows and increase the runoff duration through wet seasons. In this study, a framework to quantify the role of AGWRS in headwater tributaries on the total water balance of major basin and alteration of flow pattern in the main river has been presented. The study contains four main subroutines: rainfall-runoff model, reservoir flood routing, river analysis system and seepage analysis. The flood hydrographs with different return periods are estimated based on the climatic data and the characteristics of headwater basin. River flow analysis below the structure is carried out for two unsteady flow scenarios, first with the hydrographs of the natural system (as pre-impact: quick flood with significant peak flow) and second the altered flow hydrographs due to detention process in the reservoir (as post-impact: damped flood lower peak with longer duration time). Two sets of dynamic water surface along the river (from the location of detention structure (x=0) to the confluence point with the main river (x=L) are developed based on two hydrologic conditions as results of river analysis system. The results of framework define the impact of flood detention structure by comparing the timing, magnitude, and variability of flow. The Kamal Abad artificial groundwater recharge in Mahrlou Lake basin in Southern Iran was selected as case study to demonstrate the application of the created framework. Through the probability analysis, the return period for hydrological drought has been compared to the pre-impact and post-impact condition. The results clearly showed how embankments influence floods in tributaries and in some cases the flow reduced significantly and disappear in tributaries

Impact of managed aquifer recharge structure on river flow regimes in arid and semi-arid climates

Abstract Managed aquifer recharge (MAR) structure is widely used to expand groundwater resources. In arid regions with flash flooding, MAR can also be used as a flood control structure to decrease peak discharge of rivers. In this paper, we present a method for quantifying the role of MAR in head water systems and assess its impact on the total water balance in a river basin. The method is based on rainfall-runoff modeling, reservoir flood routing, recharge analysis and river flow analysis. For the case selected, Kamal Abad MAR in Lake Maharlou basin in southern Iran, we analyzed changes in the downstream river regime using two scenarios (with MAR and without MAR) with different return periods. The results revealed a significant impact of MAR on river flow in terms of changes in flow timing, magnitude and variability. With MAR, the ephemeral river studied became disconnected from the main stream, albeit, whereas the case without MAR, floods with return period higher than 10 years would be connected to the downstream. Even though, MAR structures are useful in arid and semi-arid climates for irrigation water supply, their placing and designing need more attention. The developed method can be used to assess the impacts of MAR on river flow and find the best location for it to make the connection of the ephemeral river and downstream river, an issue which has not received much attention in hydrological research

Impacts of gold mine effluent on water quality in a pristine sub-Arctic river

Abstract Impacts of mining on water quality are a great concern in the Arctic region. This study evaluated the impact of pre-treated mine effluent on river water quality. The study was conducted along the Seurujoki River in sub-Arctic Finland, which is impacted by Kittilä gold mine. The study analyzed water quality and hydrological data upstream and downstream of the mining area over an eight-year period, including a tailing dam leakage event in 2015. The analysis focused on water quality determinants such as electrical conductivity (EC), sulfate, antimony, manganese, and total nitrogen (Ntotal). Descriptive statistics on river water at four stations along the river corridor showed negative impacts of mining activities on the recipient water body. In order to find an indicator for water quality, correlation analysis between the water quality determinants was carried out. It identified EC as a good indicator for continuous water quality monitoring, especially to detect mining accidents such as partial failure of a tailings dam. The results showed increasing contaminant concentrations due to mining as more mine effluent was generated over time. A linear mixed model was developed to predict the coefficient of different elements affecting EC at river water monitoring stations impacted by mining effluents. The results provide new information on how to assess mining water impacts and plan future water quality monitoring

An index-based approach for assessment of upstream-downstream flow regime alteration

Abstract River regulation is challenging when there is diverse upstream and downstream interest, leading to regional and international conflict. However, quantifying the upstream-downstream flow regime changes and their causes are given less consideration in the river basin. In this study, we presented three new ratios for downstream-upstream low flow contribution (DUL), downstream-upstream high flow contribution ratio (DUH), and meteorological-hydrological drought ratio (MHD), for an integrated assessment of flow regime alteration across the river basin. To test the methods, we compared flow regime alteration upstream and downstream in the Ceyhan basin in central Turkey, which was significantly modified by agriculture between 1984 and 2018 (the irrigated area increased 2.8-fold, rainfed farming decreased by 67.6%). Our analysis revealed a clear change in the contribution of low and high flow seasons to annual flow in the last station of the river at Misis after 1984, but no considerable change in upstream tributaries. In the last decade (2005–2014) and the second half (1995–2014) of the study, the frequency of hydrological droughts increased, while meteorological droughts followed a stationary pattern. Evaluation of the impact of anthropogenic activities on river regime (by comparing flow regime characteristics after 1984 with those from 1975 to 1984 as post- and pre-impact periods) revealed low to incipient impact upstream (Hanköy, Karaahmet, and Kadirli river headwaters), severe impact below the Aslantaş dam in the basin center, and moderate impact at the last station on the Ceyhan river. The new metrics provide supplementary information on the flow regime alteration in the basin and can be introduced as a novel quantitative measure to recognize the driving factor of droughts