Thesis (MTech (Civil Engineering))--Cape Technikon, 1992. / In the Western Cape, gully ("donga") erosion is characteristic of the Swartland area where the effects of the problem have reached spectacular dimensions. In 1942 the Social and Economic Planning Council commissioned an investigation into the distribution and prevention of gully erosion. This investigation was led by Professor W J Talbot of the University of Cape Town, with the collaboration of researchers from the University of Stellenbosch. This led to the "Swartland and Sandveld" publication in August 1945. Little progress has since been made. The gullies identified by Prof Talbot's team remain to this day. In most cases they have grown even longer and deeper. The present investigation aims to study a typical network in one catchment area and to propose measures for the reclamation or stabilization of gullies. Such measures must not only be effective but also economically justifiable. In reclaiming or stabilizing a donga, a key factor is the establishment of a foundation structure. Such a structure is essential for supporting semi-permanent structures and promoting the growth of grass and bushes. At present, however, no satisfactory methods are known for the design and construction of supporting walls In narrow, deep dongas, other than those methods that require a rock foundation. Furthermore, conventional methods would require a buttress of length 17 m for a retaining wall of height 4,4 m. The amount of concrete needed, would clearly be excessive. It is therefore one of the aims of this study to develop a retaining wall with a relatively short buttress. If finances permit, the retaining structure, will be built and the stabilization process carefully monitored for possible applications in the future.

Between 1865 and 1915, arroyos developed in the southwestern United States across diverse hydrological, ecological and cultural settings. That they developed simultaneously has encouraged the search for a common cause-- some phenomenon that was equally widespread and synchronous. There are few southwestern streams for which we have even a qualitative understanding of timelines and processes involved in initiation and extension of historic arroyos. Tucson's Santa Cruz River, often cited in the arroyo literature, offers a unique opportunity to chronicle the arroyo legacy and evaluate its causes. The present study reconstructs both the physical and cultural circumstances of channel entrenchment along the Santa Cruz River. Primary data include newspaper accounts, notes and plants of General Land Office surveys, eyewitness accounts, legal depositions, and repeat photography. On the Santa Cruz River, arroyo initiation and extension happened during relatively wet decades associated with frequent warm episodes in the tropical Pacific (El Niño conditions). Intensified El Niño activity during the period 1864-1891 may be symptomatic of long-term climatic change, perhaps indicative of global warming and destabilization of Pacific climate at the end of the Little Ice Age. During this period all but one of the years registering more than three days with rain exceeding 2.54 cm (1 in) in Tucson were El Niño events. The one exception was the summer of 1890, when the central equatorial Pacific was relatively cold but when prevailing low-surface pressures and low-level winds nevertheless steered tropical moisture from the west coast of Mexico into southern Arizona. In the twentieth century, catastrophic channel widening was caused by floods during El Niño events in 1905, 1915, 1977 and 1983. The Santa Cruz River arroyo formed when climatic conditions heightened the probabilities for occurrence of large floods in southern Arizona. Inadequate engineering of ditches that resulted in abrupt changes in the longitudinal profile of the stream further augmented probabilities that any one of these floods would initiate an arroyo. In the future, changing flood probabilities with low-frequency climatic fluctuations and improved flow conveyance due to intensified land use and channel stabilization will further complicate management of the arroyo in an increasingly urbanized floodplain.

La calidad del agua de muchos ríos y arroyos se ve amenazada por las distintas actividades que el hombre realiza en las cuencas. Dada la importancia de la preservación y restauración de este valioso recurso, surge la necesidad de obtener nuevas herramientas que permitan evaluar de manera rápida, sencilla y fiable la calidad del agua, no limitándose sólo al análisis de sus características físico químicas, sino también a partir de las respuestas de la biota a las condiciones de su entorno. Por su ubicuidad, riqueza, sedentarismo y longevidad, los macroinvertebrados resultan apropiados como indicadores. En la presente investigación se evaluó la calidad del agua de arroyos pampeanos vinculados a distintos usos del suelo: urbano, industrial agrícola, ganadero y recreativo. En los arroyos Martín, El Pescado, Zapata y Buñirigo se estudió la calidad del agua desde diversas perspectivas, abarcando tanto aspectos bióticos como abióticos (variables fisicoquímicas del agua y características hidrológicas del cauce). Estos últimos incluyeron medidas tomadas en distintos niveles de organización, que van desde la bioquímica hasta los ensambles de macroinvertebrados, pasando por los individuos y haciendo énfasis en aspectos poblacionales de Hyalella curvispina (Crustacea: Amphipoda) y Pomacea canaliculata (Coenogastropoda: Ampulariidae). Los muestreos en esos arroyos se realizaron entre 2009 y 2010. En ellos se midieron parámetros fisicoquímicos y se analizó la calidad del hábitat físico (características del cauce y su vegetación) y de la biota (composición de los ensambles de macroinvertebrados, abundancias de especies sensibles y tolerantes e índices bióticos. A partir de los resultados de estas variables, se pudo establecer un orden decreciente de los arroyos en función de su calidad del agua: El Pescado > Zapata > Martín > Buñirigo. Simultáneamente, en esos arroyos se estudiaron rasgos poblacionales de P. canaliculata y H. curvispina como ser: densidad, biomasa, estructura etaria, proporción de sexos, fecundidad, fertilidad, crecimiento y supervivencia (los últimos tres sólo en P. canaliculata). Pese a que algunos de estos parámetros están influenciados por características del hábitat, la mayoría de los rasgos poblacionales analizados de ambas especies evidenciaron diferencias interpoblacionales que en general se correspondieron con los lo esperado según la calidad del agua. Alteraciones en el metabolismo de los individuos pueden repercutir en niveles de organización superiores alterando, por ejemplo, los valores normales de crecimiento y fecundidad. Dada la utilidad del estudio de la composición bioquímica para evaluar múltiples factores de estrés, tanto naturales como antropogénicos, se analizó el contenido de lípidos, proteínas y carbohidratos en huevos y tejidos (glándula de albumen y glándula digestiva) de hembras de P. canaliculata provenientes de los arroyos Martín, El Pescado, Zapata y Buñirigo. Las proporciones de lípidos, proteínas y carbohidratos en general fueron bajas en todos los tipos de muestras y evidencian poca relación con la calidad del agua, con una mayor variabilidad en la glándula digestiva. No obstante, las muestras del arroyo Martín presentaron valores más bajos que los de otros arroyos de estas sustancias, sugiriendo un peor estado nutricional. Esto concuerda con las menores tallas, tasas de crecimiento, fecundidad y fertilidad de los caracoles en este arroyo. Si bien estos resultados podrían ser consecuencia de la contaminación, no se descarta un posible efecto ligado al valor alimenticio de las macrófitas disponibles en ese arroyo. Con el fin de obtener otra herramienta de monitoreo, también se realizó una experiencia de exposición in situ con neonatos de P. canaliculata en los arroyos periurbanos El Gato, Rodríguez y Martín (los dos primeros muy contaminados) para evaluar la supervivencia frente a distintas calidades de agua. Estos caracoles mostraron ser sensibles a la contaminación, ya que en los arroyos más impactados se registró una mayor mortalidad que el sitio menos contaminado y en el control de laboratorio. Por lo tanto, se propone calibrar y validar esta herramienta en estudios de calidad del agua y monitoreo de arroyos pampeanos. El enfoque de esta investigación, abordada a través de múltiples niveles de organización, permitió obtener mayor información acerca del estado de los cuerpos de agua estudiados y discriminar los rasgos poblacionales que podrían constituir buenas herramientas para la evaluación de la calidad del agua por ser más sensibles. Asimismo, se destaca la necesidad de evaluar la calidad de los ecosistemas con un enfoque holístico, contemplando la interacción de los macroinvertebrados con las variables ambientales que operan en la regulación de sus poblaciones.

In Ecuador it has been recently noticed a relevant increase of interest on the conservation of natural resources, especially on the aquatic ecosystems, due to the high levels of biodiversity and ecosystem services that they provide. Among such ecosystems, the watersheds corresponding to headwaters are suffering increasing human pressures which exert negative effects on the ecosystem structure, composition and functioning, but the knowledge about such effects is still scarce. This dissertation focused on natural and nearly pristine streams of two Andean watersheds in the Southern Ecuador, between 2,900 and 3,730 metres above sea level. The main objectives were; 1) to examine the patterns of the structure and composition of the aquatic macroinvertebrate communities and its relation with the dominant riparian vegetation; 2) to analyse the influence of the fundamental environmental factors on the structure and density of the EPT communities (Ephemeroptera, Plecoptera, Trichoptera), during periods without relevant hydrological disturbances; 3) to determine the main hydrological indices influencing the temporal dynamics of the aquatic communities at the mesohabitat scale; 4) to analyse the temporal variation of the main macroinvertebrate taxa during periods of maintained low flows in different types of habitat. To achieve these goals, different sampling methods were implemented, involving data collection regarding riparian vegetation, physico-chemical properties of the water, hydrology, hydraulics and aquatic macroinvertebrates during 40 months. Concerning the spatial patterns, the target streams showed very similar environmental and biological characteristics which determine the presence of a low number of taxa and the dominance of very few of them; some of those large-scale factors were the type of riparian vegetation and geology. The analyses at lower spatial scale in four streams showed differences in the community at mesohabitat and microhabitat scale. Specifically, it was demonstrated the critical influence of variables related with flow strength (velocity, Froude number, shear stress) on the presence and density of some taxa; such relations could be explained by the hydromorphological traits of the organisms to resist the flow, and other traits related with their feeding habits. Concerning the variation in time, it was demonstrated the critical role of the hydrological patterns in the temporal dynamics of the community. Specifically, the frequency and magnitude of high flows exert important effects on the densities of some taxa as well as on community metrics. The high-flow events produce the dragging of part of the community, even of some taxa adapted to swift water, producing a balancing effect in the community due to the reduction of the few dominant taxa. The analyses focused on the low-flow periods only, indicated the recovery in the proportions of the pioneer taxa (familia Chironomidae). However, these low flows and the increase of water temprature exerted a negative influence on the community, both on very frequent taxa (Chironomidae, Girardia, Hyalella) and on other taxa with more sensitivity to low flows (Ecuaphlebia). The increase of temperature pose negative effects on some sensitive taxa but it allows a faster development of some organisms with a multivoltine life-history. Finally, it is important to continue with these studies to get a better knowledge about the responses of the macroinvertebrate community to different scenarios of stream flow in the high mountain streams (annual cycles of extreme low or high flows). Such knowledge is fundamental for a eco-hydrological and sustainable management of these sensitive ecosystems, facing important threats such as climate change and flow regulation, and it is the base for environmental flows assessments. Besides, the biological characteristics and the ecology of many species is still a relevant field to be developed in this region. / Hoy en día en el Ecuador existe un mayor interés por la conservación de los recursos naturales, y especialmente por los ecosistemas acuáticos por la alta biodiversidad que albergan y los servicios ambientales que proporcionan al hombre. Entre ellos están las cuencas hídricas de cabecera, sometidas a una creciente presión antropogénica y a posibles efectos negativos en la estructura, composición y funcionamiento del ecosistema fluvial, aún poco conocidos en la región Andina. La comprensión de dichos efectos requiere primero el estudio de condiciones prístinas de referencia, incluyendo los análisis de la variación espacial y temporal de las comunidades. Por ello, se ejecutó esta investigación en arroyos cuasi-prístinos ubicados entre los 2,900 a 3730 metros de altitud en dos cuencas hidrográfica andinas al sur de Ecuador. Los objetivos fundamentales fueron: (1) Examinar los patrones de variación de la estructura y composición de las comunidades de macroinvertebrados acuáticos según el tipo de cobertura vegetal dominante en las riberas; (2) analizar la influencia de los principales factores ambientales en la estructura y densidad de las comunidades de EPT (Ephemeroptera, Plecoptera, Trichoptera) durante períodos sin eventos hidrológicos elevados; (3) conocer los principales indicadores hidrológicos determinantes de la dinámica temporal de las comunidades acuáticas a escala de mesohábitat; y (4) analizar la variación de los principales taxones dominantes de la comunidad durante los caudales bajos según distintos tipos de hábitats. Para el cumplimiento los objetivos anteriores, se ejecutaron diferentes metodologías que implicaron la recolección de información sobre la vegetación de ribera, físico-química del agua, hidrología, hidráulica y macroinvertebrados acuáticos durante 40 meses. A nivel espacial, se encontró que estos arroyos de cabecera cuasi-prístinos con un buen estado de conservación comparten muchas de las características ambientales y biológicas, las cuales condicionan la presencia de un bajo número de taxones y el dominio de pocos grupos en estos ecosistemas de montaña debido a factores de gran escala, tales como la altitud, y específicamente por el tipo de cobertura vegetal y geología de la cuenca. Posteriormente, a mayor detalle, los análisis mostraron diferencias a escala de mesohábitat y microhábitat. Específicamente, se demostró que las variables relacionadas con la fuerza del flujo influyen de modo decisivo en la presencia y densidad de algunos macroinvertebrados. En cuanto a la variación en el tiempo, se observó que el patrón hidrológico es un factor clave en la dinámica temporal de las comunidades acuáticas. En concreto, la frecuencia y la magnitud de los caudales punta o picos actúan sobre la densidad de los taxones y métricas de la comunidad. Estos eventos altos de caudal causan un arrastre parcial sobre toda la comunidad, inclusive sobre los taxones adaptados a condiciones altas de flujo, dando como resultados un mejor equilibrio de la comunidad debido al descenso de los pocos taxones dominantes. Posteriormente, el análisis por separado en los períodos de caudal bajo indicó una recuperación de las proporciones de los taxones pioneros (familia Chironomidae) de estos ecosistemas. Sin embargo, se pudo detectar una cierta influencia negativa de estos niveles bajos de flujo y a su vez al incremento de la temperatura en la comunidad bentónica, tanto para los organismos habituales en estos arroyos (Chironomidae, Girardia, Hyalella) como otros más sensibles (Ecuaphlebia) a las condiciones mínimas de caudal. Finalmente, es importante continuar con estos estudios con el objeto de conocer mejor la respuesta de la comunidad a diversos escenarios de regímenes de flujo (períodos anuales secos y muy húmedos) en estos ecosistemas acuáticos de montaña, siendo la base para una gestión eco-hidrológica y sostenible, ante las amenazas que sufren estos / Avui en dia a l'Equador existeix un major interès per la conservació dels recursos naturals, i especialment pels ecosistemes aquàtics, per l'alta biodiversitat que alberguen i els serveis ambientals que proporcionen a l'esser humà. Entre aquests estan les conques hídriques de capçalera, sotmeses a una creixent pressió antropogènica i a possibles efectes negatius en l'estructura, composició i funcionament de l'ecosistema fluvial, encara poc coneguts a la regió andina. La comprensió de tals efectes requereix, en primer lloc, l'estudi de les condicions primigènies de referència, incloent les anàlisis de la variació espacial i temporal de les comunitats. Per això mateix, s'executà aquesta recerca en rierols quasi-primigenis ubicats entre els 2,900 i 3,730 metres d'altitud en dues conques hidrogràfiques andines, al sud d'Equador. Els objectius fonamentals foren: (1) examinar els patrons de variació de l'estructura i composició de les comunitats de macroinvertebrats aquàtics segons el tipus de cobertura vegetal dominant a les riberes; (2) analitzar la influència dels principals factors ambientals en l'estructura i densitat de les comunitats de EPT (Ephemeroptera, Plecoptera, Trichoptera) durant períodes sense esdeveniments hidrològics elevats; (3) conèixer els principals indicadors hidrològics determinants de la dinàmica temporal de les comunitats aquàtiques a escala de mesohàbitat; i (4) analitzar la variació dels principals taxons dominants de la comunitat durant els cabals baixos segons distints tipus d'hàbitats. Per al compliment dels objectius anteriors, s'executaren diferents metodologies que implicaren la recol·lecció d'informació de vegetació de ribera, físico-química de l'aigua, hidrologia, hidràulica, i macroinvertebrats aquàtics durant 40 mesos. A nivell espacial, es va trobar que aquests rierols de capçalera quasi-primigenis amb un bon estat de conservació comparteixen moltes de les característiques ambientals i biològiques, les quals condicionen la presencia d'un baix nombre de taxons i el domini de pocs grups en aquests ecosistemes de muntanya degut a factors de gran escala, com ara l'altitud, i específicament el tipus de cobertura vegetal i geologia de la conca. Posteriorment, a un major detall, les anàlisis mostraren diferències a escala de mesohàbitat i microhàbitat. Específicament, es demostrà que les variables relacionades amb la força del flux (velocitat, número Froude i tensió tallant) influeixen de forma decisiva en la presència i densitat d'alguns macroinvertebrats. Pel que fa a la variació en el temps, es va observar que el patró hidrològic és un factor clau en la dinàmica temporal de les comunitats aquàtiques. En concret, la freqüència i la magnitud dels cabals punta o pics actuen sobre la densitat dels taxons i mètriques de la comunitat. Aquests esdeveniments d'alts cabals causen un arrossegament parcial sobre tota la comunitat, inclusivament sobre els taxons adaptats a condicions altes de flux, donant com a resultat un millor equilibri de la comunitat a causa del descens dels pocs taxons dominants. Posteriorment, l'anàlisi per separat en els períodes de cabal baix va indicar una recuperació de les proporcions dels taxons pioners (família Chironomidae) d'aquests ecosistemes. No obstant, es va poder detectar una certa influència negativa d'aquests nivells baixos de flux i al mateix temps a l'increment de la temperatura, en la comunitat bentònica, tant per als organismes habituals en aquests rierols (Chironomidae, Girardia, Hyalella) com d'altres més sensibles (Ecuaphlebia) a les condicions mínimes de cabal. Finalment, és important continuar amb aquests estudis amb l'objectiu de conèixer millor la resposta de la comunitat a diversos escenaris de règims de flux (períodes anuals secs i molt humits) en aquests ecosistemes aquàtics de muntanya, base per a la bona gestió eco-hidrològica i sostenible, davant les amenaces que pateixen aque / Vimos Lojano, D. (2017). Influencia de las condiciones hidráulicas e hidrológicas en la variación espacial y temporal de las comunidades de macroinvertebrados acuáticos en ríos altoandinos de cabecera al sur de Ecuador [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/86217 / TESIS

Lau Wai Kee Albert. / "Architecture Department, Chinese University of Hong Kong, Master of Architecture Programme 2000-01, design report." / On double leaves. / Includes bibliographical references. / Chapter Chapter 1 --- Prologue --- p.1 / Definition of the unseen space --- p.2 / Unseen space in the city --- p.3 / Chapter Chapter 2 --- Justification of selected unseen space --- p.4 / Definition of nullah --- p.6 / Surface transformation of the nullah --- p.8 / People perception of the nullah --- p.10 / People perception of wastewater --- p.12 / Chapter Chapter 3 --- Justification of site selection --- p.15 / Site analysis --- p.18 / Transportation character --- p.22 / Chapter Chapter 4 --- Physical identity of nullah --- p.25 / Intrinsic meaning of nullah --- p.26 / Chapter Chapter 5 --- Philosophy of nullah --- p.30 / Concept --- p.34 / Project mission --- p.38 / Conceptual strategy --- p.39 / Chapter Chapter 7 --- Philosophical meaning of water --- p.46 / People perception to water --- p.50 / Basic concept in water space design --- p.52 / Chapter Chapter 8 --- Precedent study --- p.56 / Urban rivers --- p.57 / Local rivers --- p.66 / Chapter Chapter 9 --- Design ideas --- p.68 / Appendix / Water quality of Kai Tak nullah --- p.75 / Annual rainfall --- p.76 / "Interview with Dr. Chung, Dept. of Biology, CUHK" --- p.78 / Biblography --- p.80

From the Proceedings of the 1971 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 22-23, 1971, Tempe, Arizona / The early Spanish explorers did not lean toward rivers and boats. Bred in the culture of an arid land, they naturally explored with horses or by foot, leaving boats and rafts to the English and French. No historical records reveal any Spanish desires or attempts to control river flow or harness desert water resources on any appreciable scale. Yet they transformed the Sonoran desert into a productive garden land never before achieved by indigenous peoples. Pueblos were built on river banks where alluvial fans could be easily irrigated. Small arroyo check dams diverted water into wells and town tanks, while larger diversion dams were built to draw water into canals for crop irrigation. The dams were designedly weak and efficient only to the point of diverting sufficient water for the pueblo. There is no concept of storing water in reservoirs or lakes for periods of scarcity, but only of tapping enough water during periods of excess flow. All surplus water was allowed to flow downstream for the use of others in their struggle for survival. In this way the Spanish achieved a balance between human needs and the limited resources of the desert. The records of the Mexicans and the Anglos have been much more exploitive and destructive.

[Portion of abstract]: Sediment dynamics are influenced by transformed landscape connectivity in catchments worldwide. The upper Thina catchment, an important high rainfall resource in the northern Eastern Cape, South Africa, is an example of where ongoing subsistence farming on communal land has led to overgrazing and trampling that has initiated large erosive features (e.g. gullies) and river incision. The formation of gullies led to increased hillslope-channel connectivity and the resultant river incision decreased the channel-valley fill connectivity. These two changes in connectivity led to increased sediment export from the catchment that has various down-stream ecological and socio-economic impacts. This study investigates how the change in hillslope-channel and channel-valley fill connectivity has altered the sediment dynamics in the Vuvu catchment, a headwater tributary of the Thina River. A combination of methods were used to assess the changes in hillslope-channel and channel-valley fill connectivity. High resolution aerial images were used to map source features, such as fields, gullies, sheet erosion, landslides, roads and livestock tracks. Topographic and geological characteristics of the source features were extracted using a Geographic Information System. Furthermore, hillslope-channel pathways, such as the natural drainage network, continuous gullies, discontinuous gullies, roads and livestock tracks were mapped and analysed in terms of topographic and geological characteristics. Historic aerial images were assessed to calculate the date the larger gullies began forming. Recent aerial photos and cross sectional surveys of the valley fill were combined to map the various sediment sinks. Particle size and organic content were analysed for flood bench cores and terrace samples. The chronology of the flood benches was determined using unsupported Pb-210 and Cs-137 dating, and determined for the terraces using Optically Stimulated Luminescence dating. Quantitative and qualitative sediment tracing approaches, using mineral magnetic properties, were used to trace the origin of suspended sediment (collected during flood events), sediment stored in the flood benches and sediment stored in the terraces. Hydrological monitoring was used to assess the potential to store sediment on flood benches along the valley fill through flood bench inundation frequency. Hydrological and hydraulic modelling extended the measured inundation frequencies to a 73 year period and other cross sections along the valley fill. Furthermore, a future scenario of an increased vegetation cover and reduced hillslope-channel connectivity was assessed in terms of channel-valley fill inundation frequency.

From the Proceedings of the 1971 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 22-23, 1971, Tempe, Arizona / The pre-Columbian Hohokam Indians occupied the major river drainages of central Arizona, and have been the subject of much intense archaeological research. Evidence indicates that the Hohokam began using river water for crop irrigation about 300 B.C., and modified and improved their irrigation systems over time, until the maximum extent of these systems was achieved about 900 a. D. Two types of water control seem to have been utilized: (1) the direct exploitation of rivers through the use of irrigation canals, (2) indirect use through controlled runoff within microdrainages at higher elevations before it reached the rivers. At first, probably only those parcels of land with optimal soils and drainage were used, but apparently population increases fostered by agriculture itself, combined with increasing social and political complexity, necessitated more and more exploitation of marginal lands. Eventually soil problems increased, imposing severe limitations on agriculture. These involved salt and alkali accumulation due to inadequate drainage, soil density and water logging. Additionally, the extension of cropping required the clearing of natural vegetation, which resulted in increased erosion and decreased available native food resources for periods when crops failed. The culture vanished completely about 1450 a. D., probably mainly because of their manner of river exploitation for irrigation. More recent archaeological studies are concentrating not only on river use but also on river abuse.

From the Proceedings of the 1973 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - May 4-5, 1973, Tucson, Arizona / The geohydrology of a portion of the Santa Catalina Mountains including the definition of aquifer systems in the foothills was studied in order to calculate groundwater recharge to the Tucson basin. This underlying groundwater aquifer is the only source of Tucson, Arizona's water supply. A well network, well logs, geologic profiles, and a water level contour map were used as source information. Recharge was found to occur in some sections of washes and close to the mountains where washes cross or coincide with faults. Significant recharge to sand and gravel aquifers occurs directly through faults and joints. Little of the surface runoff is thought to recharge local aquifers because of low permeability layers beneath the alluvium and the short duration of the flows. Recharge calculation using the Darcy equation was subject to considerable error; but flow net analysis showed the total recharge to be 336 acre-feet per year representing about 50 acre feet per mile of mountain front per year.

A report on the vegetation of the Cabeza Prieta NWR, with tables giving statistical representations of the vegetation associations.