Streams are classified into perennial, intermittent, and ephemeral streams based on flow durations. Perennial stream is the basic network, while intermittent or ephemeral stream is the expanded network. Connection between perennial stream and base flow at the mean annual scale exists since one of the hydrologic functions of perennial stream is to deliver runoff even in low flow seasons. The partitioning of precipitation into runoff and evaporation at the mean annual scale, on the first order, is captured by the ratio of potential evaporation to precipitation (Ep/P called climate aridity index) based on the Budyko hypothesis. The primary focus of this thesis is the relationship between base flow and perennial stream density (Dp) in the Budyko framework. In this thesis, perennial stream density is quantified from the high resolution National Hydrography Dataset for 185 watersheds; the climate control (represented by the climate aridity index) on perennial stream density and on base flow is quantified; and the correlation between base flow and perennial stream density is analyzed. Perennial stream density declines monotonically with the climate aridity index, and an inversely proportional function is proposed to model the relationship between Dp and Ep/P. This monotonic trend of perennial stream density reconciles with the Abrahams curve, and the perennial stream density is only a small portion of the total drainage density. The dependences of base flow ratio (Qb/P) and the normalized perennial stream density on the climate aridity index follow a similar complementary Budyko-type curve. The correlation coefficient between iv the ratio of base flow to precipitation and perennial stream density is found to be 0.74. The similarity between the base flow and perennial stream density reveals the co-evolution between water balance and perennial stream network.

Text in Afrikaans / Die private persoon het sekere bevoegdhede betreffende die arrestasie en die gebruik van geweld tydens arrestasie van lede van die publiek wat misdade pleeg/gepleeg het. Hierdie bevoegdheid spruit uit sowel die gemenereg as die wettereg. Kragtens die Suid-Afrikaanse Strafproseswet word hierdie bevoegdhede gereel deur aa 42 en 49. Oewerbewoners as eienaars van grand is geregtig op die onverstoorde gebruik en genot van hulle eiendom. Daarteenoor is kanovaarders ook daarop geregtig om op openbare ri vi ere vir wedvaarte te oefen. Di t is egter belangrik om vas te stel of die portage van kano's op die oewer insidenteel is tot die reg om op die rivier te vaar. Ewewig moet bewerkstellig word tussen die botsende belange. Die Waterwet 54 van 1956 behoort gewysig en vereenvoudig te word, aangesien Suid-Afrika nie slegs op die RomeinsHollandse reg kan staatmaak nie - ons waterprobleme staan direk teenoor die van die Nederlande. / The private person has certain powers regarding the arrest and the use of force to effect the arrest of members of the public who have committed/are committing offences. These powers are derived from either common law or statutory law. In terms of the South African Criminal Procedure Act these powers are regulated by ss 42 and 49. Riparian owners are entitled to the undisturbed use and enjoyment of their property. On the other hand, canoeists are also entitled to practise on public rivers. It is important, however, to ascertain whether portage of canoes on the river bank is incidental to the right of canoeing on the river. A balance should be struck between these conflicting interests. The Water Act 54 of 1956 should be amended and simplified, since South Africa cannot rely on Roman Dutch law alone - our water problems are the complete opposite of those in the Netherlands. / Criminal & Procedural Law / LL.M. (Straf- en Strafprosesreg)

Text in Afrikaans / Die private persoon het sekere bevoegdhede betreffende die arrestasie en die gebruik van geweld tydens arrestasie van lede van die publiek wat misdade pleeg/gepleeg het. Hierdie bevoegdheid spruit uit sowel die gemenereg as die wettereg. Kragtens die Suid-Afrikaanse Strafproseswet word hierdie bevoegdhede gereel deur aa 42 en 49. Oewerbewoners as eienaars van grand is geregtig op die onverstoorde gebruik en genot van hulle eiendom. Daarteenoor is kanovaarders ook daarop geregtig om op openbare ri vi ere vir wedvaarte te oefen. Di t is egter belangrik om vas te stel of die portage van kano's op die oewer insidenteel is tot die reg om op die rivier te vaar. Ewewig moet bewerkstellig word tussen die botsende belange. Die Waterwet 54 van 1956 behoort gewysig en vereenvoudig te word, aangesien Suid-Afrika nie slegs op die RomeinsHollandse reg kan staatmaak nie - ons waterprobleme staan direk teenoor die van die Nederlande. / The private person has certain powers regarding the arrest and the use of force to effect the arrest of members of the public who have committed/are committing offences. These powers are derived from either common law or statutory law. In terms of the South African Criminal Procedure Act these powers are regulated by ss 42 and 49. Riparian owners are entitled to the undisturbed use and enjoyment of their property. On the other hand, canoeists are also entitled to practise on public rivers. It is important, however, to ascertain whether portage of canoes on the river bank is incidental to the right of canoeing on the river. A balance should be struck between these conflicting interests. The Water Act 54 of 1956 should be amended and simplified, since South Africa cannot rely on Roman Dutch law alone - our water problems are the complete opposite of those in the Netherlands. / Criminal and Procedural Law / LL.M. (Straf- en Strafprosesreg)

Base flow recession curve during a dry period is a distinct hydrologic signature of a watershed. The base flow recession analysis for both streamflow and spring flow has been extensively studied in the literature. Studies have shown that the recession behaviors during the early stage and the late stage are different in many watersheds. However, research on the transition from early stage to late stage is limited and the hydrologic control on the transition is not completely understood. In this dissertation, a novel cumulative regression analysis method is developed to identify the transition flow objectively for individual recession events in the well-studied Panola Mountain Research Watershed in Georgia, USA. The streamflow at the watershed outlet is identified when the streamflow at the perennial stream head approaches zero, i.e., flowing streams contract to perennial streams. The identified transition flows are then compared with observed flows when the flowing stream contracts to the perennial stream head. As evidenced by a correlation coefficient of 0.90, these two characteristics of streamflow are found to be highly correlated, suggesting a fundamental linkage between the transition of base flow recession from early to late stages and the drying up of ephemeral streams. At the early stage, the contraction of ephemeral streams mostly controls the recession behavior. At the late stage, perennial streams dominate the flowing streams and groundwater hydraulics governs the recession behavior. The ephemeral stream densities vary from arid regions to humid regions. Therefore, the characteristics of transition flow across the climate gradients are also tested in 40 watersheds. It is found that climate, which is represented by climate aridity index, is the dominant controlling factor on transition flows from early to late recession stages. Transition flows and long-term average base flows are highly correlated with a correlation coefficient of 0.82. Long-term average base flow and the transition flow of recession are base flow characteristics at two temporal scales, i.e., the long-term scale and the event scale during a recession period. This is a signature of the co-evolution of climate, vegetation, soil, and topography at the watershed scale. The characteristics of early and late recession are applied for quantifying human impacts on streamflow in agricultural watersheds with extensive groundwater pumping for irrigation. A recession model is developed to incorporate the impacts of human activities (such as groundwater pumping) and climate variability (such as evapotranspiration) on base flow recession. Groundwater pumping is estimated based on the change of observed base flow recession in watersheds in the High Plains Aquifer. The estimated groundwater pumping rate is found consistent compared with the observed data of groundwater uses for irrigation. Besides streamflow recession analysis, this dissertation also presents a novel spring recession model for Silver Springs in Florida by incorporating groundwater head, spring pool altitude, and net recharge into the existing Torricelli model. The results show that the effective springshed area has continuously declined since 1988. The net recharge has declined since the 1970s with a significant drop in 2002. Subsequent to 2002, the net recharge increased modestly but not to the levels prior to the 1990s. The decreases in effective springshed area and net recharge caused by changes in hydroclimatic conditions including rainfall and temperature, along with groundwater withdrawals, contribute to the declined spring flow.