This dissertation shows a novel strategy using soil matric potential based irrigation to improve water productivity of rice cultivation which is a case study from Sri Lanka. Study contains research component and a crop modelling component.:Introduction Fundamentals and Scientific Background Literature Review New Methods for Improving Water Productivity in Rice Cultivation Results and Discussion Conclusions and Outlook

Die wesentlichen Einflussgrößen auf den Wasserverbrauch von Pflanzen sind klimatischer Art, die Pflanze selbst und der Wasserhaushalt des Bodens. Als wichtige klimatische Einflussgrößen sind das Sättigungsdefizit der Luft bzw. die Dampfdruckdifferenz zwischen Blatt und Luft und die Einstrahlung zu nennen. Die Einstrahlung beeinflusst das Gewächshausklima und hat eine direkte Wirkung auf die Öffnungs- und Schließbewegung der Stomata. Die Bodenfeuchte ist sowohl im Hinblick auf die Wasseraufnahme der Pflanzen als auch bei einem Anbau im gewachsenem Boden auf eine mögliche Sickerwasserbildung und damit eine Nährstoffauswaschung von Bedeutung. Die im Gewächshausanbau eingesetzten Prozessleitsysteme berücksichtigen die Wechselwirkungen der Einflussfaktoren auf den Wasserumsatz eines Pflanzenbestandes nur bedingt. Einzelne Parameter wie z.B. die Einstrahlungssumme oder das Matrixpotential des Bodens werden zwar zur Steuerung der Bewässerung verwendet, eine Kombination der Einflussfaktoren wie z.B. die Anpassung der Einstrahlungssumme an das Pflanzenwachstum muss bisher vom Anwender vorgenommen werden. Zur Darstellung der Zusammenhänge des Wasserumsatzes eines Pflanzenbestandes im Gewächshausanbau wurde in den experimentellen Untersuchungen der Wasserumsatz in Abhängigkeit der Bodenfeuchte (Matrixpotential), der klimatischen Größen (Einstrahlungssumme, Sättigungsdefizitsumme und Dampfdruckdifferenzsumme) an Lactuca sativa, Brassica oleracea var. gongylodes und Cucumis sativus untersucht. Aufgrund des hohen Bestimmtheitsmaß und niedrigen Variationskoeffizienten sowie der Übertragbarkeit auf verschiedene Bodenarten und Kulturen ist die Matrixpotentialmessung als Führungsgröße für die Bewässerungssteuerung zu verwenden. Da die häufig eingesetzten Tensiometer bzw. Tensioschalter, bauartbedingt Schwächen aufweisen sind diese Sensoren durch übergeordnete Modellrechnungen zu kontrollieren. Dazu ist die Einstrahlungssumme, Sättigungsdefizitsumme und der Gießabstand zu verwenden. Die klimatischen Parameter müssen über entsprechende Modellrechnungen und der Analyse bereits ausgeführter Gießtakte dem Pflanzenwachstum angepasst werden. Nachdem bereits einige Prozessleitsysteme die für die Bewässerung- und Klimasteuerung notwendigen Hardwarekomponenten in ein System integriert haben, muss die Verknüpfung auf Softwareebene realisiert werden. Hierzu müssen die Kontrollstrategien d.h. die Softwareroutinen entsprechend schnell angepasst werden können. Aufgrund der in den letzten Jahren gesteigerten Leistungsfähigkeit bieten sich hierzu Prozessleitsysteme auf PC-Basis an. / The fundamental parameters determining the water consumption of plants are the climate, the plant itself and the soil water supply. The important climatic parameters are the water saturation deficit of the air or more correctly the water vapour pressure difference between leave surface and air, and the solar irradiation. The solar irradiation influences the greenhouse climate and has therefore an immediate effect on the opening and closing of the stomata. The soil humidity is important for both the water absorbtion of a plant and - when cultivating in soil - the possible losses of water and nitrogen into deeper soil layers causing environmental pollution of the ground water. The computer systems used for controlling the irrigation in greenhouses do not take the interactions of the influence coefficients on the water exchange of plants sufficiently into account. Single parameters like the irradiaton sum or the water tension are used for controlling irriagaton, but the combination of different influence factors like the adaption of the irradiation sum to the plant growth must be done by the user so far. Several scientific trials were carried out to describe the water consumption of plants in greenhouses. The water consumption is defined by the water tension of the soil, the irradtiotion sum, the water vapour pressure deficit sum and water vapour pressure difference sum. For the trials the plants Lactuca sativa, Brassica oleracea var. gongylodes and Cucumis sativus were used. The soil water tension measured by tensiometers proved to be the best parameter for controlling irrigation because of the highest stability index and the lowest variation coefficient as well as the transferability of this parameter to different soil types and plants. Because the construction of tensiometers and tensioswitches can cause problems, a superordinated model calculation has to control the sensors. This calculation is based on the parameters irradiation sum, water pressure deficit sum and irrigation intervals. The climatical control parameters must be adapted to the plant growth by using adequate model calculations and the analysis of previous irrigation events After a lot of computer systems for greenhouse process controlling integrated the hardware components necessary for irrigation and climatic control, this has to happen with the software basis as well. A quick update of the Software must be possible. Personal computers can be used because of the improved capacity.

No description available.

Mit der Intensivierung der landwirtschaftlichen Produktion gewinnen Pumpstationen für die Be- und Entwässerung landwirtschaftlicher Nutzflächen zunehmend an Bedeutung. Zur Beseitigung schädlicher Bodennässe werden offene Gräben oder Dränrohrleitungen angelegt, welche das Wasser bei nicht vorhandener Vorflut einem Entwässerungsschöpfwerk zuleiten. Dieses Schöpfwerk fördert das Wasser aus einem Speicherraum (Mahlbusen) in den Vorfluter. In der DDR sind zahlreiche derartige Entwässerungsschöpfwerke vorhanden. (...):1. Einleitung S. 1 2. "Konventionelle" Pumpstationen S. 4 3. Pumpstationen mit Heberauslässen S. 9 4. Ökonomischer Vergleich S. 22 5. Vergleich mit anderen Anwendungsarten des Hebers S. 32 6. Gegenwärtiger Stand der hydraulischen Berechnung von Heberauslässen und Aufgabenstellung für eigene Untersuchungen S. 43 7. Hydraulische Versuche an Heberauslässen S. 47 8. Betriebsverhalten und hydraulische Berechnung von Heberauslässen S. 56 9. Zusammenfassung und Ausblick S. 186 10. Literatur-, Konsultations- und Exkursionsverzeichnis S. 190 11. Symbolverzeichnis S. 200

Durch den in den letzten Jahren in Deutschland stark ausgeweiteten Spargelanbau wird der Kostendruck auf die Erzeuger immer größer. Um eine Spargelfläche ökonomisch erfolgreich zu bewirtschaften sind Anbauempfehlungen die auf einer objektiven Grundlage beruhen unersetzlich. Eine Möglichkeit hierzu ist das Messen der Reservekohlenhydratkonzentration (RKH-Konzentration) in den Speicherwurzeln. Ein sehr großer Nachteil dieser Methode ist, dass die Speicherwurzelmasse, die einen erheblichen Einfluss auf die verfügbare Gesamtmenge an Reservekohlenhydraten hat unberücksichtigt bleibt. Hinsichtlich der Wurzelmasse und der Wurzelverteilung im Boden bestanden bislang große Wissenslücken. Um den Einfluss der Bewässerung auf die Wurzelmasse und die Wurzelverteilung zu ermitteln, wurde ein Praxisversuch angelegt. Zu bestimmten Zeitpunkten in der Vegetationsperiode wurden Proben auf einer bewässerten und einer unbewässerten Variante entnommen. In der bewässerten Variante waren zu jedem Zeitpunkt signifikant mehr Speicherwurzeln vorhanden. Auch die Speicherwurzelfrischmasse war signifikant größer. In der Tiefenverteilung unterschieden sich jedoch die Varianten nicht. Auch in Gefäßversuchen konnten diese Ergebnisse bestätigt werden. Die Faserwurzelverteilung unter Praxisbedingungen unterschied sich jedoch erheblich von der Speicherwurzelverteilung. In der bewässerten Variante war der Boden im untersuchten Profil komplett mit Faserwurzeln durchwachsen, während in der unbewässerten Variante die Faserwurzeln lediglich in den oberen Bodenschichten zu finden waren. In Gefäßversuchen durchwurzelten die Faserwurzeln unabhängig von der Bewässerungssteuerung das gesamte Bodenvolumen. Unter mehrjährigen Praxisbedingungen lag die RKH-Konzentration in der unbewässerten Variante immer über der Konzentration in der bewässerten Variante. Die Gesamtmenge an RKH lag jedoch aufgrund der größeren Speicherwurzelmasse in der bewässerten Variante höher. Daher muss bei der Verwendung der RKH-Methode als Steuerinstrument im Spargelanbau unbedingt auch die Speicherwurzelmasse berücksichtigt werden. / The cultivation of asparagus in Germany has strongly expanded over the last years. Hence the cost pressure is increasing vastly on the producers. For the cultivation of asparagus, impartial cultivation recommendations are necessary. One possibility is measuring the carbohydrate concentration (CHO-concentration) in the storage roots. A great disadvantage of this method is that the root mass, which has a substantial influence on the total quantity of available carbohydrates, remains unconsidered. Regarding to the root mass and the distribution of roots in the soil so far large gaps in the grower’s knowledge are existent. In order to determine the influence of the irrigation on the root mass and the distribution of roots, a trial was prepared. Samples of a watered and an unwatered variant were taken at certain points in the vegetation period. In the watered variant were significantly more storage roots were present at each time. Further the storage root fresh mass was significantly bigger. However, in the vertical distribution the variants did not differ, which could also be confirmed in container trials. The distribution of fibre roots under practical conditions did indeed differ substantially from the storage root distribution. In the watered variant the soil profile was completely filled with fibre roots, whereas in the unwatered variant the fibre roots were only found in the upper soil layer. In container trials the fibre roots were distributed throughout the entire soil volume independently of the irrigation control. Under practical conditions the CHO concentration was always higher for the unwatered variant compared to the watered variant. However, the total quantity of CHO was higher in the watered variant due to the larger storage root mass. Therefore the storage root mass has to be considered when using the CHO method as an instrument in the cultivation of asparagus.

Heute werden nur etwa 20% der landwirtschaftlich genutzten Flächen auf der Erde bewässert (World Resources Institute, 2003). Doch die Bewässerungslandwirtschaft produziert schon 40% aller Nahrungsmittel weltweit. Zur Sicherung der Ernährung der Weltbevölkerung – derzeit leiden 800 Mio. Menschen an Unterernährung – verfolgen Welternährungsorganisation (FAO) und die UNESCO das Ziel, den Anteil bewässerter Flächen in den nächsten 30 Jahren um weitere 20% zu erhöhen (UNESCO, 2003). Die beschriebene Geschichte der extensiven Bewässerung in der Antike könnte sich wiederholen, denn weltweit sind 30% der Flächen, die zur Bewässerungslandwirtschaft geeignet sind, von der Versalzung bedroht, falls nicht angemessen bewässert wird. Überbewässerung tritt oft bei den am weitesten verbreiteten Methoden der Oberflächenbewässerung auf. Diese seit der Antike bekannten Verfahren, wie beispielsweise die in dieser Arbeit näher behandelte Furchenbewässerung, sind einfach anzuwenden, aber schwierig zu steuern. Denn es offenbaren sich zwei große Probleme, wenn für einen Bewässerungsvorgang die beiden erforderlichen Steuerparameter Bewässerungszeit und Intensität bestimmt werden sollen. Erstens muss die Bewässerung mit den zu berechnenden Steuergrößen gleichzeitig • für eine gleichmäßige Verteilung des Wassers auf dem Feld sorgen, • den aktuellen Wasserbedarfs der Pflanzen decken, • langfristig das Anheben des freien Grundwasserspiegels verhindern, • bei Bedarf eine Auswaschung von überschüssigen Salzen (engl. leaching requirement) in der Wurzelzone bewirken und nicht zuletzt • mit dem geringsten möglichen Volumen an Wasser erfolgen. Um diese Zielstellungen zu erreichen, ist im allgemeinen die Lösung eines schwierigen nichtlinearen Optimierungsproblems notwendig.

Policy makers adopt irrigated agriculture for food security, since irrigation doubles crop production. Therefore, the development of large irrigation systems has a long history in many places worldwide. Although large-scale irrigation schemes play an important role in improving food security, many schemes, especially in Africa, do not yield the expected outcomes. This is related to poor water management, which is generally due to a lack of effective evaluation and monitoring. The objective of this study, therefore, is to propose a new methodology to assess, evaluate and monitor large-scale irrigation systems. Information on irrigation indicators is needed to enable the evaluation of irrigation performance. The evaluation is the first and the most significant step in providing information about how it is performing. After reviewing extensive literature, a list of indicators related to the performance of irrigation, rainwater supply and productivity is suggested. The irrigation efficiency indicators Relative Irrigation Supply (RIS) and Relative Water Supply (RWS) are selected. Potential rainwater supply to crops can be tested based on the Moisture Availability Index (MAI) and the Ratio of Moisture Availability (RMA). Water productivity can be assessed by Crop Yield (Y) and Water Use Efficiency (WUE). However, the central problem facing large-scale irrigation schemes is always the lack of data, which calls for the development of a new method of data acquisition that allows evaluation and monitoring. Remote Sensing (RS) technology makes it possible to retrieve data across large areas. Two different approaches via RS, the Normalized Difference Vegetation Index (NDVI) and Actual Evapotranspiration (ETa), can be utilized for monitoring. The well-known Vegetation Condition Index (VCI), derived from the NDVI, is modified (MVCI) to allow a qualitative spatio-temporal assessment of irrigation efficiency. MVCI takes into account crop response to water availability, while ETa indicates whether water is used as intended. Furthermore, the assessment of the possible hydrological impact of the irrigation system should be considered in the evaluation and monitoring process. The Sudanese Gezira Scheme of 8,000 square kilometers in the Nile Basin, where performance evaluation and monitoring are absent or poorly conducted, is no exception. This research takes the large-scale irrigation of the Gezira Scheme as a case study, as it is the largest scheme, not only in the Nile Basin but also in the world, under single management. The first long-term historical evaluation of the scheme is conducted for the period 1961–2012 rather than only on a short-time scale as is the common practice. An increase in RIS and RWS values from 1.40 and 1.70 to 2.23 and 2.60, respectively, since the 1993/94 season shows decreasing irrigation efficiency. MAI and RMA for summer crops indicate a promising rainfall contribution to irrigation in July and August. The Gezira Scheme achieves low yield and WUE in comparison to many irrigation schemes of the globe. Low productivity is mainly due to poor distribution and irrigation mismanagement. This is indicated by the 15-year MVCI spatio-temporal analysis, which shows that the northern part of the scheme experiences characteristic drought during the summer crop season. Although MVCI can be considered a monitoring tool, the index does not deduct the soil water content, and water could be wasted and available in other ways (e.g. water depressions). Spatio-temporal information for ETa is required to better quantify water depletion and establish links between land use and water allocation. However, several RS models have been developed for estimating ETa. Thus, improving the understanding of performance of such models in arid climates, as well as large-scale irrigation schemes, is taken into account in this study. Four different models based on the energy balance method, the Surface Energy Balance Algorithm for Land (SEBAL), Mapping EvapoTranspiration at High Resolution with Internalized Calibration (METRIC™), Simplified Surface Energy Balance (SSEB) and MOD16 ET are applied in order to determine the optimal approach for obtaining ETa. Outputs from these models are compared to actual water balance (WB) estimates during the 2004/05 season at field scale. Several statistical measures are evaluated, and a score is given for each model in order to select the best-performing model. Based on ranking criteria, SSEB gives the best performance and is seen as a suitable operational ETa model for the scheme. SSEB subsequently is applied for summer and winter crop seasons for the period 2000–2014. Unfortunately, one of the limitations faced in the current research is the absence of validation data on a regional scale. Therefore, the assessment focuses on spatial distribution and trends rather than absolute values. As with the MVCI distribution, the seasonal ETa for the Gezira Scheme is higher in the southern and central parts than in the northern part. This confirms the robustness of the developed MVCI. To avoid using absolute values of ETa, the ratio of ETa from agricultural areas (ETagr) to the total evapotranspiration (ET) from the scheme (ETsum) is calculated. The ETagr/ETsum ratio shows a descending trend over recent years, indicating that the water is available but not being utilized for agricultural production. This study shows that SSEB is also useful for identifying the location of water losses on a daily basis. Around 80 channels are identified as having leakage problems for the 2013/14 crop season. Such information is very useful for reducing losses at the scheme. In addition, Rainwater Harvesting (WH) is addressed and found to be applicable as an alternative solution for accounting for rainfall in irrigation. It is seen that these management scenarios could save water and increase the overall efficiency of the scheme. It is possible to save 68 million cubic meters of water per year when the overall irrigation efficiency of the scheme is improved by only 1%. A level of efficiency of 75% is predicted from the proposed management scenarios, which could save about 2.6 billion cubic meters of water per year. In conclusion, the present study has developed an innovative method of identifying the problems of large-scale schemes as well as proposing management scenarios to enhance irrigation water management practice. Improved agricultural water management in terms of crop, water and land management can increase food production, thereby alleviating poverty and hunger in an environmentally sustainable manner.

Policy makers adopt irrigated agriculture for food security, since irrigation doubles crop production. Therefore, the development of large irrigation systems has a long history in many places worldwide. Although large-scale irrigation schemes play an important role in improving food security, many schemes, especially in Africa, do not yield the expected outcomes. This is related to poor water management, which is generally due to a lack of effective evaluation and monitoring. The objective of this study, therefore, is to propose a new methodology to assess, evaluate and monitor large-scale irrigation systems. Information on irrigation indicators is needed to enable the evaluation of irrigation performance. The evaluation is the first and the most significant step in providing information about how it is performing. After reviewing extensive literature, a list of indicators related to the performance of irrigation, rainwater supply and productivity is suggested. The irrigation efficiency indicators Relative Irrigation Supply (RIS) and Relative Water Supply (RWS) are selected. Potential rainwater supply to crops can be tested based on the Moisture Availability Index (MAI) and the Ratio of Moisture Availability (RMA). Water productivity can be assessed by Crop Yield (Y) and Water Use Efficiency (WUE). However, the central problem facing large-scale irrigation schemes is always the lack of data, which calls for the development of a new method of data acquisition that allows evaluation and monitoring. Remote Sensing (RS) technology makes it possible to retrieve data across large areas. Two different approaches via RS, the Normalized Difference Vegetation Index (NDVI) and Actual Evapotranspiration (ETa), can be utilized for monitoring. The well-known Vegetation Condition Index (VCI), derived from the NDVI, is modified (MVCI) to allow a qualitative spatio-temporal assessment of irrigation efficiency. MVCI takes into account crop response to water availability, while ETa indicates whether water is used as intended. Furthermore, the assessment of the possible hydrological impact of the irrigation system should be considered in the evaluation and monitoring process. The Sudanese Gezira Scheme of 8,000 square kilometers in the Nile Basin, where performance evaluation and monitoring are absent or poorly conducted, is no exception. This research takes the large-scale irrigation of the Gezira Scheme as a case study, as it is the largest scheme, not only in the Nile Basin but also in the world, under single management. The first long-term historical evaluation of the scheme is conducted for the period 1961–2012 rather than only on a short-time scale as is the common practice. An increase in RIS and RWS values from 1.40 and 1.70 to 2.23 and 2.60, respectively, since the 1993/94 season shows decreasing irrigation efficiency. MAI and RMA for summer crops indicate a promising rainfall contribution to irrigation in July and August. The Gezira Scheme achieves low yield and WUE in comparison to many irrigation schemes of the globe. Low productivity is mainly due to poor distribution and irrigation mismanagement. This is indicated by the 15-year MVCI spatio-temporal analysis, which shows that the northern part of the scheme experiences characteristic drought during the summer crop season. Although MVCI can be considered a monitoring tool, the index does not deduct the soil water content, and water could be wasted and available in other ways (e.g. water depressions). Spatio-temporal information for ETa is required to better quantify water depletion and establish links between land use and water allocation. However, several RS models have been developed for estimating ETa. Thus, improving the understanding of performance of such models in arid climates, as well as large-scale irrigation schemes, is taken into account in this study. Four different models based on the energy balance method, the Surface Energy Balance Algorithm for Land (SEBAL), Mapping EvapoTranspiration at High Resolution with Internalized Calibration (METRIC™), Simplified Surface Energy Balance (SSEB) and MOD16 ET are applied in order to determine the optimal approach for obtaining ETa. Outputs from these models are compared to actual water balance (WB) estimates during the 2004/05 season at field scale. Several statistical measures are evaluated, and a score is given for each model in order to select the best-performing model. Based on ranking criteria, SSEB gives the best performance and is seen as a suitable operational ETa model for the scheme. SSEB subsequently is applied for summer and winter crop seasons for the period 2000–2014. Unfortunately, one of the limitations faced in the current research is the absence of validation data on a regional scale. Therefore, the assessment focuses on spatial distribution and trends rather than absolute values. As with the MVCI distribution, the seasonal ETa for the Gezira Scheme is higher in the southern and central parts than in the northern part. This confirms the robustness of the developed MVCI. To avoid using absolute values of ETa, the ratio of ETa from agricultural areas (ETagr) to the total evapotranspiration (ET) from the scheme (ETsum) is calculated. The ETagr/ETsum ratio shows a descending trend over recent years, indicating that the water is available but not being utilized for agricultural production. This study shows that SSEB is also useful for identifying the location of water losses on a daily basis. Around 80 channels are identified as having leakage problems for the 2013/14 crop season. Such information is very useful for reducing losses at the scheme. In addition, Rainwater Harvesting (WH) is addressed and found to be applicable as an alternative solution for accounting for rainfall in irrigation. It is seen that these management scenarios could save water and increase the overall efficiency of the scheme. It is possible to save 68 million cubic meters of water per year when the overall irrigation efficiency of the scheme is improved by only 1%. A level of efficiency of 75% is predicted from the proposed management scenarios, which could save about 2.6 billion cubic meters of water per year. In conclusion, the present study has developed an innovative method of identifying the problems of large-scale schemes as well as proposing management scenarios to enhance irrigation water management practice. Improved agricultural water management in terms of crop, water and land management can increase food production, thereby alleviating poverty and hunger in an environmentally sustainable manner.

No description available.

Die vorliegende Untersuchung hat in der Nordosten Hoch-ebene Stadt Nova Hartz, spielend in der erzbischöflichen Region Porto Alegre – Hauptstadte des Bundesland Rio Grande do Sul- stattgefunden . Das Ziel wurde die aktuelle Situation der umweltliche Verwitterung des Bach Arroio Grande durch Beschreibung und Übersicht des naturelles Zeiger zu erkennen. Das untersuchte Gelände fasst Teil des Arroio Grande Unterbecken um, das zum Bewässerungsbecken des Rio dos Sinos gehört. Zur physichen Daten nahm man eine Forschung bei ehmaliger Einwohner zu, um die soziale und umweltliche Landschaft von mitte des XX Jahrhundert bis heutzutage zu bilden. Die Wiederaufbau des pflanzliche Decke in dem Hang den Bergen wegen der Verzicht auf landwirtschaftliche Arbeit, als positiv gesehen und die Verwitterung des Wasserstoffreserven, als negative Ansicht, wurden in dieser Forschung festgestellt, beschreibt und analysiert. Wurde nachgeprüft, dass, trotz der menschliche Intervention, die die Änderung in dynamischen Gleichgewicht des ökologisches System verursacht, das Gelände naturelle Faktoren zeigt, die zu seiner Schwäche beitragen, und dass, das Verwitterungen zeugt. Diese Verwitterungen sind durch die menschliche unangemessene Akten über diese schwacheUmwelt schneller und verstärkt. Die Zeigen von naturellen Verwitterungen, so wie Erosion, Auswaschung des Flussufer und Versandung den Wasserlaufen, kommen im ländlichen Gegend am meistens vor. Andere Zeigen Verwitterungen, wie Fehlen von wimperichem Wald und Entleerung häuslichen und industriellen Abfall, kommen stärker im städischen Gegend vor. Einige Vorschläge stehen in dieser Arbeit, in der Absicht neue Handlungen, die der Aufschlag den Zeigen minimizieren, zu ermöglichen, und so, zukunftliche Problemen, die in anderen Städten mit ähnlichen Kennzeichen als Nova Hartz vorkommen, zu verhindern. / O presente estudo foi realizado no município de Nova Hartz, localizado a nordeste da encosta do planalto médio, na região metropolitana de Porto Alegre, capital do Rio Grande do Sul. Objetivou-se diagnosticar a situação atual da degradação ambiental do arroio Grande, através da descrição e mapeamento de indicadores naturais e antrópicos. A área pesquisada abrange parte da sub-bacia do arroio Grande, pertencente à bacia hidrográfica do rio dos Sinos. Acrescentou-se aos levantamentos físicos, uma pesquisa junto aos moradores antigos com o objetivo de reconstruir o cenário sócio-ambiental desde meados do século XX até os dias atuais. A recuperação da cobertura vegetal nas encostas de morros devido ao abandono das atividades agrícolas, como aspecto positivo e a degradação dos recursos hídricos como aspecto negativo, foram constatados, descritos e analisados na presente pesquisa. Constatou-se que, apesar da intervenção humana estar causando alterações no equilíbrio dinâmico dos ecossistemas, a área apresenta fatores naturais que contribuem para sua fragilidade, gerando degradações cujos processos são acelerados e acentuados pelas atividades humanas inadequadas sobre esses ambientes frágeis. Os indicadores de degradação de origem natural, como erosões, solapamento das margens e assoreamento dos cursos de água, estão mais presentes nas áreas rurais. Indicadores de degradação de origem antrópica, como ausência de mata ciliar e despejo de efluentes domésticos e industriais, se fizeram presentes de forma mais acentuada nas áreas urbanizadas. Os resultados das análises de alguns parâmetros indicadores da qualidade das águas do arroio Grande mostraram uma significativa diminuição da qualidade das águas na área urbana e a jusante dela. Algumas sugestões foram somadas ao presente trabalho, no intuito de possibilitar ações que possam minimizar os impactos dos indicadores mapeados e evitar futuros problemas já ocorridos em outras cidades com características semelhantes à Nova Hartz. / The present study was carried out in the county (municipality) of Nova Hartz, localized to the northeast of the slope of the medium highlands, in the metropolitan region of Porto Alegre, capital of Rio Grande do Sul. Our goal was to diagnose the real situation of the environmental degradation of the rivulet Arroio Grande, through the description and the mapping of of natural and antropic indicators. The area under survey includes part of the sub-basin of Arroio Grande, belonging to the hydrographic basin of the river Rio dos Sinos. To the physical data we added a survey with the older dwellers aiming at reconstructing the socioenvironmental scenario since the middle of the 20th century till our days. The recovery of the vegetal cover on the moutain slopes due to the abandonment of agricultural activities, as a positive aspect and the degradation of the hydric resources as a negative aspect, were verified, described and analyzed through the perception of old dwellers of the place. It was verified that, in spite of the human intervention bringing about alterations on the dynamic balance of the ecosystems, the area presents natural factors contributing to its fragility, bringing about degradations whose processes are accelerated and accentuated by inadequate human activities on these fragile environments. These degradation indicators of natural origin, like erosion, underwash of brook banks and the silting up of water courses , are more present in rural areas. Degradation indicators like the absence of ciliary woods and the inflow of domestic and industrial wastewaters are much more accentuated in urbanized areas. Some suggestion were added to the present paper with the intent of allowing actions which might minimize the impact of the mapped indicators and help avoid future problems as have already happened in other towns with characteristics similar to Nova Hartz´s.